M.272

LINEAR ELECTRON ACCELERATOR STUDIES A.E.C. Contract AT(O4-3)-21

(Project Agreement No. 1)

and

PROPOSED TWO-MILE ACCELE OR PROJECT A.E.C. Contract AT (04-3) -363

Combined Status Report 1 April EQ 30 June 1941

M.L. Report No. 827 M Report No. 272

July 1961

W. W. HANSEN LABORATORIES OF PHYSICS STANFORD UNIVERSITY STANFORD, CALIFORNIA

M- 272

LINEAR ELECTRON ACCELERATOR STUDIES

A. E. C. Contract AT( 04-3)-21 (Project Agreement No. 1)

and

PROPOSED TWO-MILE ACCELEFULTOR PROJECT

A. E. C. Contract AT( 04-3)-363

Combined Status Report

1 A p r i l to 30 June 1961

M.L. Report No. 827 M Report No. 272

July 1961

W. W. Hansen Laboratories of Physics Stanford University Stanford, California

X .

XI n

XI1 .

XI11 .

XIV *

xv .

XVI . XVII . XVIII .

XIX .

High-power klystron windows . . . . . . . . A . Window life test stand . . . . . . . . B . Recirculator window tests . . . . . . . C . Move to new building . . . . . . . . . D . Other window work . . . . . . . . . . . Modulator studies . . . . . . . . . . . . . A . Subcontract system development program

B . Project development activities . . . . Vacuum system . . . . . . . . . . . . . . . A . Mark IV conversion . . . . . . . . . . B . Component design . . . . . . . . . . . C . Feasibility studies . . . . . . . . . . D . Problems to be resolved . . . . . . . .

. . . . . . .

. . . . . . .

. . . . . . .

. . . . . . .

. . . . . . .

. . . . . . .

. . . . . . .

. . . . . . .

. . . . . . .

. . . . . . .

. . . . . . .

. . . . . . .

. . . . . . . E . Conclusions . . . . . . . . . . . . . . . . . . . . . Support and alignment studies . . . . . . . . . . . . . . A . General . . . . . . . . . . . . . . . . . . . . . . . B . Support . . . . . . . . . . . . . . . . . . . . . . . C . Alignment . . . . . . . . . . . . . . . . . . . . . . Control system studies . . . . . . . . . . . . . . . . . A . General studies during the last quarter . . . . . . . B . Instrumentation and control signals . . . . . . . . . General rf studies . . . . . . . . . . . . . . . . . . . A . Constant-gradient accelerator structure . . . . . . . B . Conical disk structure . . . . . . . . . . . . . . . Research area design and related problems . . . . . . . . A . Radiation shielding . . . . . . . . . . . . . . . . . B . Accelerator heating . . . . . . . . . . . . . . . . . C . Beam handling systems . . . . . . . . . . . . . . . . Plant engineering activities . . . . . . . . . . . . . . AC power system . . . . . . . . . . . . . . . . . . . . . Cooling-water system . . . . . . . . . . . . . . . . . . A . Two-mile accelerator . . . . . . . . . . . . . . . . B . MarkIV . . . . . . . . . . . . . . . . . . . . . . . C . Project M Building . . . . . . . . . . . . . . . . . D . Research and development . . . . . . . . . . . . . . Heating and ventilating . . . . . . . . . . . . . . . . .

14 14 15 15 18 18 21

23 23 23 23 23 24 25 25 26 26 2'7 2'7

29 31 31 31 32 32 33 33 34 36 38 38 39 39 39 40

..

LIST OF FIGURES

Page 1. Window disk test assembly using shrinking technique . . . . . 17 2. Ignitron assembly--experimental design #1 . . . . . . . . . . 20

3. Comparison of calculated percent of ionization and measured normalized values . . . . . . . . . . . . . . . . . . . . . . 22

Preliminary Laboratory site plan . . . . . . . . . . . . . . 35

- iv -

T

I.

I. INTR ODUCT I ON

This Status Report covers the work of two Atomic Energy Commission contracts held by Stanford University.

objectives of each contract is given below. A brief description of the

Contract AT( 04-3)-21, Project Agreement No. 1. This contract has

been in effect since July, 1953. properties and anomalies of the present Mark I11 and Mark IV linear electron accelerators at Stanford, and improvement of the various compo-

nents of these machines.

tract are E. L. Ginzton and R. B. Neal.

The objectives include studies of the

The responsible investigators for this con-

Contract AT(04-3)-363. This contract covers the period from 1 Sep- tember 1990 to 30 June 1961. engineering and development work for the proposed Stanford two-mile

linear electron accelerator. Among the specific objectives are master

planning of the accelerator site, buildings and laboratories; develop- ments of components and sub-systems; and the procurement of test models

of particular components that will lead to initiation of construction without delay. The Mark IV accelerator is being converted to a model section of the proposed two-mile accelerator, incorporating those compo-

nents and techniques intended for later use with the larger machine.

The objectives include initial design,

Because the work of the two contracts is closely related, it has

been decided to report their activities in this combined Status Report.

For greater simplicity and clarity in reporting, no attempt has been

made within the body of the report to attribute the various activities

to one or the other of the contracts.

The two-mile accelerator project ("Project M") has not yet been authorized by the Congress. If the project is eventually authorized,

the construction program will be divided into two parts:

accelerator itself and its related technical environment; and (2) the

more conventional work associated with site preparation, buildings,

structures, utilities, etc. To assist with the latter activities,

Stanford has retained the services, under subcontract, of the firm of

Aetron-Blume-Atkinson, a joint venture consisting of Aetron, a division

of Aerojet-General Corporation; John A. Blume and Associates, Engineers; and the Guy F. Atkinson Company. In these reports this architect-engineer- management firm is often referred to as "ABA."

(1) the

- 1 -

11.

11. MARK IV PROGRAM

During the past quarter work has proceeded on the installation of

mechanical and electrical components f o r the Mark IV accelerator. All

components appear to be satisfactory. A large manifold used for evacu-

ating the outlets has been operated at 2 x torr. Effort currently

is being made to complete all systems f o r a preliminary beam test during

the next quarter.

A stock-control and inventory system f o r Mark IV has been designed and implementation has been started.

cataloged in order of frequency of use, rather than by part and nomen- clature. It is intended that this catalog system w i l l be evaluated for

possible future application to Project M.

Under the new system,parts are

- 2 -

111.

111. ACCELERATOR STRUCTURE STUDIES

A. RAD1 OFREQUENCY STUDIES

The tes t setup f o r t he measurement of gassing e f f ec t s , cw heat

experiments, and peak power heating experiments described i n the last

Status Report’ i s nearly completed.

cavi ty f o r use i n t h i s equipment a r e being car r ied out, and it appears t h a t t he f i rs t experimental r e s u l t s w i l l be obtained within the next

few weeks.

Cold measurements on t h e first tes t

Work i s being completed on t h e pa r t s f o r electroforming two 2 10-foot constant-gradient sections. A s previously reported, these are

the f i rs t constant-gradient sect ions, and w i l l be ul t imately in s t a l l ed

i n Mark I V f o r high-power evaluation of t h e i r performance. To f a c i l i -

tate the taking of data f o r t h e constant-gradient input and output

couplers, two 18-inch lengths of the constant-gradient disk-loaded

waveguide have been made, one f o r t h e input end and one f o r the output

end.

B. EUCTROFORMING

The r e s u l t s obtained using t h e electroforming method described i n

t h e las t Status Report (M-260) have been so successful t h a t a small

evaluation p l a t ing setup i s being made which w i l l allow 10-foot lengths

t o be electroformed. The tanks f o r t h i s f a c i l i t y are i n place, and

work i s progressing toward completion of t he wiring and i n s t a l l a t i o n

of t h e other necessary equipment.

C. BRAZING The model flame furnace, described i n the last Status Report

(~-260), has yielded excellent r e s u l t s with sect ions two f e e t long.

are now i n t h e process of building a fu l l - sca l e model of t he furnace

which w i l l allow the brazing of 10-foot lengths.

We

1. Status Report, M Report No. 260, Stanford University, April 1961.

2. Status Report, M.L. Report No. 741, W. W. Hansen Laboratories of Physics, Stanford University, August 1960.

- 3 -

T

111.

D. PARTS FABRICATION A study of the various methods of fabr ica t ing the d e t a i l pa r t s t h a t

go in to electroforming and brazing assemblies has been completed.

r e s u l t s indicate t h a t a boring machine spec i f i ca l ly tooled t o make these

pa r t s i s the bes t approach.

experimental programs, a boring machine has been procured and i s now

being in s t a l l ed ,

The

In order t o carry out our evaluation and

- 4 -

IV .

IV. BEAM DYNAMICS STUDIES

A. GENERAL BEAM DYNAMICS

During the last quarter a computer program was written for optical

ray-tracing of electron trajectories in an accelerator. The program

represents various accelerator components, such as uniform accelerating sections, misalignments, steering magnets, quadrupole lenses, etc., as

matrices which transform the dynamical coordinates (px, p , 67, x, y, 8t)

from one reference plane to another. Two versions are available: ver-

sion I is first order, and version I1 is second order in the dynamical coordinates,

Y

The computer program is expected to be useful for work on: 1. The design and investigation of strong-focusing guide-field

systems in the presence of misalignments, stray magnetic fields and

other perturbing effects.

2. The effects of second-order aberrations on final beam quality.

B. BEAM LOADING STUDIES A report on transient beam loading in uniform structures in the

3 presence of phase modulation has been published as a Project M report.

3. R. H. Helm, "Transfent Beam Loading Calculations for Linear Electron Accelerators, Part I: Uniform Structures; Phase Modulation," M Report No. 266, Stanford University, May 1961,

- 5 -

V.

V. INJECTION SYSTEM

A. BUNCHING

It has been shown t h a t it i s possible t o bunch electrons t o within

a phase in t e rva l of 16' (energy spread of 1 percent) through t h e use of

two uniform sect ions of disk-loaded waveguide, the first sect ion having

a phase veloci ty v = O.gc, and the second sect ion having a phase ve- P

l o c i t y v = c. With t h e correct choice of parameters, over 80 percent

of t h e electrons can be bunched within

sect ion and within a 16' asymptotic phase bunch a t the end of t h e

second sect ion (which i s the f irst standard accelerator sect ion) .

4

0 P ? 43 a t t h e end of t h e first

In Sec. V of t h e las t Status Report (~ -260) , it w a s reported t h a t

i f the allowable energy spread i s reduced t o 0.1 percent, the parameters

must be modified and only 65 percent of t he electrons can be bunched

within the required 5 asymptotic phase bunch. Many combinations of

diff'erent buncher types have been studied i n an attempt t o obtain a

bunching of about 80 percent of t h e electrons within t h e 0.1 percent

energy spread. One type which present ly seems promising consis ts of

t he following elements:

0

1. A prebunching section, composed of a uniform sect ion of disk-

loaded waveguide about four free space wavelengths long, with v = 0 . 2 . P

2. A f i r s t bunching section, composed of a short uniform sect ion

of disk-loaded waveguide two t o three wavelengths long, with P

Electrons entering t h e first buncher sect ion between f 43 are

bunched in to a phase in t e rva l of 25'.

v = c. 0

3. A second bunching section, composed of a long uniform sect ion

of disk-loaded waveguide, w i t h v = c. Electrons enter ing t h e second

sect ion between f 12O30' are bunched between - 89' and - 91'. P

The f i rs t bunching sect ion requires a = 2.85 (energy gained per

wavelength over t he rest energy), and the second bunching sect ion re-

quires a = 0.42. Therefore, t he second bunching sect ion can be excited

4. Georges D8me, "Electron Bunching by Uniform Sections of Disk-Loaded Waveguide,'' M Report No. 242A, Stanford University, December 1960.

- 6 -

by t h e wave from the output of t h e f i rs t bunching section after t h e re-

quired at tenuat ion and phase s h i f t . In summary, t he bunching system

discussed above i s theore t ica l ly capable of bunching 80 percent of t he

injected electrons in to a 2 phase in te rva l ,

B. CHOPPING

0

During the past quarter an invest igat ion w a s made of the possi-

b i l i t y of chopping off a t t h e beginning of the accelerator those elec-

t rons which it i s not possible t o bunch within the required energy

spread of 0.1 p e r ~ e n t . ~

values of veloci ty modulation a t t h e input of t h e prebuncher, any

system t h a t w i l l separate electrons entering the prebuncher a t d i f f e r -

ent phase angles by means of veloci ty modulation has t o be avoided.

Therefore, t h e only chopping system tha t appears t o be desirable i s a

transverse modulation system, Each electron passing through a cavi ty

would be def lected transversely, with t h e magnitude of t h e def lect ion

depending on t h e a r r i v a l angle. By adding a screen with a hole, some

of t h e electrons can be stopped.

be focused before they en ter t h e accelerator.

promising f o r use with a high-current gun and a s ingle veloci ty modula-

t i o n buncher,

i s moderatea

Because of t he important e f f ec t of even small 6

The def lected electrons w i l l have t o

A chopping system looks

The power required by t h e transverse def lect ion cavi ty

/ 5. Renee H i r e l , "A Study of t h e Electron Bunching Problem,"

In te rna l Memorandum, M Report No, 269, Stanford University, June 1961.

6, M-260, 0p.ci-t. -.

c

- 7 -

V I .

VI. DRIVE SYSTEBI

A. RADIOFREQUENCY DRIVER The rf driver for the Mark IV accelerator has been undergoing tests

during the last quarter.

specifications under a subcontract but has so far failed to meet these specifications; further tests and modifications are planned. This work

is being carried out in conjunction with the subcontractor.

This unit has been developed to Stanford

B. SUB-BOOSTERS

Two TH 2101 klystrons, on loan from the CFTH Company of France, have been delivered. These tubes have characteristics similar to those

required for the drive system sub-boosters on the two-mile machine.

Facilities for testing these tubes will be designed and a f u l l test

program will be undertaken.

C. CONTRIBUTION TO THE MARK IV CONVERSION PROGRAM

1. Electronic Components

This has included a detailed examination of the various components,

their control and instrumentation, and layout on the control console. Design and construction of temperature-controlled ovens and regulated

current supplies for the ferrite components has been completed. Con-

sole switching circuits f o r the nunerous power monitors and the signal viewing circuits have been designed and are under construction.

2. Microwave Components

a. Accelerator sections. The tuning, matching and testing of

two 10-foot, 2n/3 electroformed sections has been completed.

b. Coaxial drive line. The testing and assembly of the coaxial

drive line has been accomplished and is in position in the Mark IV area. c. Directional couplers. The significant parameters of the high-

power waveguide-to-coaxial directional couplers have been determined,

and the units are now ready for installation. combiners for the klystrons has also been completed.

Matching of the power

- 8 -

V I .

D. TEST BUTLDING DRIVE SYSTEM

A study of t he requirements for t he rf dr ive system for the on-si te

Test Building has been made.

groups a combination of two systems has been suggested, as follows.

To meet the requirements of t he various

1. House RF Driver System

A very s t ab le rf dr iver source a t 2856 * 2 Mc/sec w i l l provide a

cw s igna l along t h e length of t he building.

booster which, i n turn, w i l l provide a pulsed s igna l t o each tes t stand

a t t h e required pulse length and r epe t i t i on rate.

un i t s w i l l be provided f o r t he tes t stands.

2.0 kw w i l l be provided a t each stand, along with a var iable a t tenuator

t o allow any lower l e v e l dr ive s ignal t o be obtained.

e r a to r w i l l be s imilar ly provided.

determined primarily by the operating frequency of t he T e s t Accelerator,

which w i l l l i m i t t he f l e x i b i l i t y of t he system. To overcome t h i s lie-

tat ion, independent tunable (f. 20 Mc/sec) sources w i l l be provided.

This w i l l feed a sub-

Two sub-booster

A maximum peak power of

The T e s t Accel-

The operating frequency w i l l b e

2.

A number of independent, portable un i t s w i l l be provided t o give a

tuning range of It 20 Mc/sec a t t he power leve ls , pulse r epe t i t i on r a t e s

and pulse lengths required. These uni t s w i l l be b u i l t from avai lable

components and w i l l not have the frequency s t a b i l i t y of the house dr iver

system.

Variable Frequency R F Driver System

The specif icat ions and various possible systems t h a t w i l l meet t he

requirements of 1 and 2, together with the required t r igger ing system,

a r e being examined. A preliminary schedule has been completed.

E. DRIVE SYSTEM SCHEDULE - PROJECT M

A de ta i led study of t he scheduling f o r t he dr ive system, from t he

research and development stage through t o i n s t a l l a t i o n and subsystem

t e s t ing , i s being conducted.

F. HIGH-POWER WAVEGUIDE

Discussions with the Vacuum Group on t h e required propert ies of t he

high-power waveguide runs from the klystron t o the accelerator sect ion

have been i n i t i a t e d .

The compatibil i ty of t h e desired rf propert ies with respect t o the

vacuum system, mechanical properties, cooling, e t c . , are being examined

and preliminary specif icat ions a r e being drawn up.

Twelve possible configurations have been suggested.

- 9 -

VII.

VII. PHASING STUDIES

A. CONTRIBUTION TO MARK IV CONVERSION PFXGRAM

Procurement of the remaining microwave components for use on the

Mark IV was accomplished during this period.

calibration of these items has been carried out.

of the component controls on the console were completed, together with the necessary switching circuits, and fabrication is proceeding.

B. BEAM INDUCTION TECHNIQUE STUDIES

Acceptance testing and

The design and layout

It has been shown that under certain conditions considerable

changes in beam current can result from quite small changes in beam

energy.

to be effectively turned off and then on with a consequent reduction

in beam energy and, hence, in beam current. A more detailed study of

this problem is presently in progress. Techniques of keeping the beam

energy constant during ntzchine operation, independent of tube failure

and phase errors, etc., are being studied by the Instrumentation and

Control Group.

The beam induction technique of phasing requires the klystron 8

Components have been installed on the Mark I11 which will enable experiments to be carried out using the beam induction technique. These experiments are planned for the early part of the next quarter.

7. K. E. Breymayer, "Problems in Beam Operation," M Report No. 255, Stanford University, May 1961.

8. M-260, op.cit., p. 12. --

- lo -

VIII.

V I I I . KLYSTRON STUDIES

During t h e last quarter, t h e Klystron Group has continued the pro-

duction of tubes t o s a t i s f y the needs of other groups, has continued

t h e move in to new f a c i l i t i e s i n t h e Project M Building, and has made

preparations f o r fabr ica t ion of tubes tha t w i l l conform t o the dimen-

s ional specif icat ions t h a t have been established.

A. TUBE CWLEMENT AND PERFORMANCE

No major changes have been attempted i n the fabr ica t ion methods or i n t h e design of t h e present klystrons t o improve t h e i r general charac-

t e r i s t i c s . Some modifications i n fabr icat ion w e r e introduced t o de-

crease the d i f f i c u l t i e s experienced with t h e copper gaskets used

between windows. The general performance of t h e tubes is s t i l l satis-

factory, although a f e w tubes have shown lower eff ic iency than w a s

measured previously on s imi la r tubes. The present complement of tubes

approaches one dozen, of which one i s being t e s t ed on a full-power

modulator.

B. SUBCONTRACTS

During the past quarter , t r i p s were made t o Sperry Gyroscope Com-

pany (Great Neck, Long Island, New York) and RCA (Lancaster, Pa.) t o

discuss both klystrons and high-pawer windaw problems.

1. A t t h e present time, Sperry has under test a klystron t h a t has

achieved the main objectives of peak power and efficiency.

t e s t i n g i t s f i rs t klystron, but t he cathode perveance i s less than

expected and accordingly the f u l l power has not been achieved.

RCA i s now

2. Both subcontractors are making progress i n window designs.

Sperry reports t ha t it has had several windows on t e s t a t high power

without f a i lu re s . RCA has a compressed-seal design for fabricat ion of

t he window tha t should make it possible t o dispense w i t h metall izing

the window and, thus, to eliminate the in te r face a t the braze jo in t .

T h i s technique might reduce rf losses i n the metall izing of t he window.

3. Representatives of both subcontractors a r e planning t o v i s i t

Stanford during t h e second week of July, a t which time they w i l l have

complete drawings of t he tubes they propose t o bui ld under the subcon-

t r a c t for del ivery t o Stanford.

- 11 -

VIII.

C. NEW FACILITIES

The move t o the new Project M Building on campus has been p a r t i a l l y

c omplet ed . 1. Shop

The Tube Shop equipment has not ye t been i n s t a l l e d s ince f a c i l i t i e s -

( e l e c t r i c i t y , gases and water) are not yet f u l l y provided.

2. Test Area

The 100-megawatt modulator purchased from Ling has been i n opera-

t i o n with two Stanford tubes.

the inter lock c i r c u i t s and t r i g g e r c i r c u i t s of t h e Modulator,which have

not permitted us t o make as fu l l use of it as ant ic ipated.

f ac tu re r has been helpful i n correct ing the d i f f i c u l t i e s .

a tube is being tested tha t we hope t o get t o f u l l peak and average

power within the next two weeks.

Many small t roubles have developed i n

The manu-

A t present,

9

3. Test Equipment

The al l -metal high-power load, which w a s being invest igated and

w a s mentioned i n t h e last Status Report ( ~ - 2 6 0 ) , proved unsat isfactory

because of rnultipactoring i n the cav i t i e s of t he load.

r a r i l y using g l a s s water - f i l l ed loads, although we have been delayed

again by g l a s s breakage and corrosion of t he water through t h e glass-to-

metal seal. T h i s has resu l ted i n loss of vacuum, time, and occasional

windows.

D. EXPERIMENTALTUBES

W e a r e tempo-

Another all-metal high-power load i s being designed.

Experimental a c t i v i t i e s included work on a beam t e s t e r and on a

spec ia l ly designed tube f o r uniform-field permanent-magnet focusing.

1. The tests of t h e fu l l - s i zed beam t e s t e r have been ca r r i ed on

during t h i s past quarter. The focusing of t he beam i n the case of

9. On June 23, t he tube operated f o r several hours without signs of d i s t r e s s under the following conditions:

Beam voltage: 225 kv Beam current: 191 Amps Beam power: 43 MW peak; 60 t o 62 kw average RF output power: about 13 Mk peak; 11.23 kw average

- 12 -

VI11 .

nonreversal f i e l d focusing appears t o be very nearly what w e had expec-

ted. On the other hand, t he reversa l focusing and periodic focusing

p o s s i b i l i t i e s appear much l e s s promising a f t e r t he tests car r ied out

with t h i s beam t e s t e r . The beam has a tendency t o blow up or t o scal lop

i n unusable fashion.

2. The shor t tube i s ready f o r bake-out and should be tested

during the next quarter; f i r s t , on anelectromagnet t h a t has been

procured f o r it, and, second, on a permanent magnet t h a t has been re-

ceived f o r use with t h i s short tube.

3. fabr ica t ion , s ince a number of disks were received ear ly i n June.

4. No addi t iona l work has been done on conductive coatings f o r

Single-disk beryllium oxide ceramic windows are now ready for

alumina windows

5 . A small program f o r design of copper gaskets for either circu-

lar o r rectangular geometry appears t o have produced good r e su l t s .

Since only a f e w gaskets have been t e s t ed , however, we do not wish t o

recommend them f o r f i n a l use i n the tubes a t t h i s time.

E. PROGRAM FOR NEXT QUARTER We expect t o move a l l Klystron Group ac t iG i t i e s i n t o the Project M

Building during July. We are s t a r t i n g a tube redesign program t o con-

form t o the general ou t l ine drawing which appeared i n the last (M-260)

Status Report.

magnet focusing on klystrons a t t h i s power l e v e l during the coming quar-

t e r . Final ly , preliminary design of the new f a c i l i t i e s i n t he Test

Accelerator Building on s i te has begun and w i l l be completed during the

next quarter

We a l s o expect t o determine the f e a s i b i l i t y of permanent-

- 13 -

c

IX .

I X . HIGH-PCXJER KLYSTRON WINDCNS

A. W I N D a W LIFE TEST STAND

The Li t ton type L 3302 klystron has been successfully used t o power

the window l i f e t e s t rack during t h i s quarter.

using two windows i n s e r i e s i n order t o simplify the operation from a

vacuum standpoint.

t i o n a l windows were added, one a t a t i m e .

new window each t i m e and allowed eas i e r operation.

a r e s i x windows i n t h e s t r ing , with equipment avai lable f o r t he addi-

t i o n of s i x more.

and the power out of t he lkst window a l l can be measured.

monitoring the temperature and rad ia t ion from t h e windows.

The tests were s t a r t e d

These windows were run t o f u l l power and then addi-

This l imited gassing t o t h e

A t present there

The power input, t he re f lec ted power from t h e input,

We are a l s o

The maximum power t o date has been approximately 10 m, with a 2.5 A t o t a l of 113 hours had been run by the end of t h e psec, 60 pps rate.

quarter, when tests w e r e stopped by failure of some of t h e modulator

components. Replacements have not a r r ived a t t h i s date. If the Ling

modulator i s avai lable (see below) w e w i l l move the tube and windows t o

t h i s un i t within t h e ne& few weeks.

B. RFCIRCULATOR WINDCXJ TESTS 10 Seven pa i r s of windows were run i n t h e double window assembly.

One window f a i l e d due t o cracking with some s l i g h t p i t t i ng .

t h e others f a i l ed , but some assemblies were not operable because of

mismatch a t high power. Some of these pa i r s were run up t o 29 Mw with-

out f a i lu re . One p a i r w a s run f o r a’bout 35 hours a t levels of 20 t o 25

Mw without mishap. W e had hoped t h a t failure might occur a t t h i s high

level.

out d i f f i cu l ty .

f a i l u r e s i n t h e ring, it i s apparent t h a t other f ac to r s are involved i n

t h e f a i l u r e s which have occurred.

None of

Another p a i r ran for a f e w hours a t 26 Mw and 26 kw, again with-

Although t h i s i s the only geometry which has produced

Two windows of t he J-type, a symmetrical s t ruc ture i n which t h e

disk i s i n the center of a cy l indr ica l guide about 7 inches long, were

10. Described i n t h e Status Report, M Report No. 246, Stanford University, January 1961.

- 14 -

Ix.

tes ted.

punctured a t tha t time.

down above 8 M w .

turing normally 0 ~ c u r s . l ~

w a l l s and the window; however, b r igh t spots sometimes appeared a t t he

t e r m i n i of t he arcs . These may have been formation of holes but, due

t o t h e damage on the window before t e s t , t h i s could not be determined.

W e a l s o t e s t ed a disk assembly made by RCA (Lancaster, Pa. ) which

These had been used on Mark I11 several years ago and w e r e both

One ran normally; t h e other had severe break-

Arcing occurred between the two areas i n which punc-

No arcing w a s observed between the metal

w a s matched with an A-type s t ruc ture .

alumina i n a s i lver-plated cylinder s imilar t o t h a t used i n t h e sapphire

t e s t s .

b i l i t y occurred.

and t h e disk a t t h i s leve l , but no damage w a s done.

t he disk 90°, r e t e s t it t o 20 M w , and then use it on the Mark I11 ac-

ce le ra tor .

C. MOVE TO NEW BUILDING

The material w a s Frenchtown

12 The window ran s a t i s f a c t o r i l y up t o 25 M w , where some ins ta -

A s l i g h t b i t of arcing occurred between the s i l v e r

We intend t o r o t a t e

The rec i rcu la tor and modulator were moved t o t h e new building a t

t h e end of t h i s quarter and, af ter a down time of a week and a ha l f ,

are now i n operation.

water sources.

nel . weeks, using t h i s modulator t o dr ive t h e klystron.

and cold tes t gear are now i n the new building.

. * .

The Ling modulator i s connected t o t h e power and

I ts i n i t i a l operation i s being handled by Ling person-

If successful, w e w i l l move the l i f e tes t stand i n the next f e w

A l l o ther personnel

D. OTHER W I N D c k J WORK

1. Sapphire Window

Further invest igat ion of t he resonances

s t ruc ture have disclosed t h a t a first order,

ex i s t s a t 2935 Mc. The resonance a t 2845 Mc

i n the sapphire window

even, TMol ghost mode

appears t o be a trapped

resonance, probably a TE mode, since a pa i r of horizontal septums

g rea t ly reduces i t s amplitude. It i s probably excited by the anisotro-

py of the 6O0-oriented sapphire disk.

11

11. Status Report, M Report No. 232, Stanford University, November 1960, p. 22.

12. M-246, Z - c i t . , pp. 24-25.

- 15 -

IX .

2. Half-Wave Window

Some work has been done on half-wave blocks of alumina of 3" di- These have a ghost mode near the operating frequency. Differ- ameter.

ent diameters will have to be used, although this will make measurements more difficult .

3. Thin Windows

We have designed a structure, similar to the model A, in which a

thin disk can be held by shrinking the structure around it (see Fig. 1).

The cylinder containing the disk is demountable, which will allow us to

replace disks easily without the expense and rf difficulties introduced

by the metal-to-ceramic seal.

disks on the assumption that, since the dielectric strength is one-half that of the disks normally used, failure will occur at about one-fourth

the power at which present windows fail.

due to charging of the disk.

materials will be tried.

These tests are being done with 1/16-inch

This assumes that failure is

If systematic failures are obtained, other

4. Coated Windows

Two new types of conducting coating, developed at Eimac, will be tested as soon as models are available. These coatings are being

applied by Eimac, without charge to Project M; on materials furnished by US.

5. Low-Gradient Window

A structure which avoids any sharp discontinuities in the vicinity

of the dielectric has been designed and is now under construction. It

consists of two disks which are self-matched. Both ends of the struc-

ture taper gradually from cylindrical to rectangular guide. The space

between the two disks is pumped by a Vacion-type pump. Initially, the

construction will be demountable and the shrinking technique, described

above, will be used.

6. Cerium Sulphide Dielectrics

Small pieces of cerium sulphide have been grown by workers at

General Atomic (San Diego). The sulphur content of this material can

be adjusted to give a wide range of conductivity, which would prevent

the material from charging. We will investigate the rf properties of this material for possible use as a window dielectric.

lease of sulphur will have to be studied, also, since it is very poisonous to oxide cathodes.

The possible re-

- 16 -

IX"

Y alignment disks Y FIG. 1--Window disk test assembly using shrinking technique.

- 17 -

T

X.

X. MODULATOR STUDIES

A. SUBCONTRACT SYSTEM DEVELOPMENT PROGRAM

During the last quarter t he subcontract w i t h RCA (Moorestown,

New Jersey) continued a t a sa t i s f ac to ry pace.

t he i n i t i a t i o n of two smaller subcontracts. A program w a s i n i t i a t e d

w i t h Shockley Transis tor Corporation f o r the development of an experi-

mental so l id - s t a t e switch capable of passing 5,000 amperes, three

microsecond pulses, and of holding off two ki lovol ts . Another contract

was i n i t i a t e d with t h e General Elec t r ic Company (Schenectady, New York)

for t h e fabr ica t ion of igni t ron tubes designed by t h i s laboratory spe-

c i f i c a l l y f o r t he pulse-switching service required by t h e Project M

modulators. The s t a tus of each of these contracts is as follows:

The last quarter a l s o saw

1. RCA

This contract has reached the s tage where a l l major e l e c t r i c a l and -

mechanical design problems have been resolved and where a l l components

a r e now i n the procurement cycle. The next major s t ep an t ic ipa tes re-

ce ip t of high-voltage components s o t h a t full-power t e s t i n g of t h e

pulse-forming network and pulse transformer can start late i n Ju ly a t

Stanford.

supply t o Stanford is expected t o be on schedule f o r l a te November of

t h i s year.

Delivery of t he first three modulators and the tes t power

2. Shocklev Sol id-s ta te Switch

During the past month we have received and tested three d i f f e ren t

versions of 4-layer diodes su i t ab le f o r 5,000 ampere service.

extended s e r i e s of tests i n our laboratory indicates t h a t t h i s approach

i s indeed feas ib le and tha t , with economical diode diameters, power

pulse currents of 8,500 amperes are admissible f o r th ree microsecond

pulses.

An

One of t h e major problems i s accommodating the r a d i a l expansion

From every indicat ion the incurred by t h e junctions a t high dut ies .

present design of t h e Shockley un i t s overcomes t h i s d i f f i cu l ty .

Certain problems inherent i n t h e 4-layer device concern the fact

t h a t some form of holding current (of t h e order of 10 amperes) i s

required t o avoid destruct ion of t h e diodes during t h e main pulse.

- 18 -

X.

We are invest igat ing various means for generating su i tab le , f l ex ib l e

c i r c u i t r y t o accomplish t h i s , and the Shockley Laboratories a r e making

considerable progress toward reducing the amount of required holding

current.

3. Igni t ron Fabrication

During the last quarter an igni t ron spec i f ica l ly designed f o r

pulse appl icat ion was fabricated by the General Elec t r ic Company i n

accordance with our detai led drawings. The experimental tube has been

shipped, and pulse t e s t s of i t s charac te r i s t ics w i l l s tart i n t h i s

laboratory on June 26.

With reference t o Fig. 2, t h e major features of the tube tha t

dis t inguish it from r e c t i f i e r devices a r e as follows:

a. In t h e new design the gradient g r id i s in tegra l ly grounded t o

t h e tube s t ruc ture , thus eliminating t h e need f o r a s e r i e s of coaxial

g r i d connection she l l s such as are found i n Type 6228 r e c t i f i e r . The

elimination of coaxial g r i d s h e l l s improves t h e radial heat t r ans fe r

from the anode and allows a subs tan t ia l reduction i n anode diameter f o r

t h e same rms current. The anode i n the new tube, however, i s made

s m a l l enough so t h a t it should run a t about >OO°C a t our rms current of

l5O amperes.

b, The anode and anode space a r e provided with su i tab le f i l l e t s

and r a d i i t o maintain a constant gradient throughout t h e voltage hold-

off space.

c. The control g r id i s of t h e intercept ing type, t ha t is, there

i s no completely open path from cathode t o anode on the tube center

l i n e , as with previous r e c t i f i e r s . This change i n construction w a s

indicated by the results of our tests on previous tubes, which showed

the nature of t h e deionizing mechanism after the pinched plasma pene-

t r a t e d the control g r id region. Early t e s t s of t h e experimental tube

w i l l confirm or deny t h e supposition upon which t h i s change was predi-

cated.

d. A molybdenum baffle has been attached t o the sh ie ld g r id t o provide more immediately adjacent deionization surface i n accordance

with the same theory.

a r ing immediately over the center l i n e s of t he three ign i te rs .

The holding anode has been made i n the form of

The

- 19 -

- 20 -

X.

anode w i l l thus a c t somewhat as a splash baffle, but a t t he same t i m e w i l l allow free electron t r a j e c t o r i e s along the center l i n e of the tube.

e. The reduction i n anode diameter and elimination of the coaxial

g r i d nests has made possible an over-al l reduction i n tube diameter,

which w i l l provide stronger focusing during discharge.

sions a r e specif ied f o r cathode-to-shield gr id spacing, namely,

16-7/32 in . and 5-11/32 in. , t h i s f o r the reason tha t only empirical

tests can determine whether o r not mechanical splashing of mercury

droplets from t h e i g n i t e r region w i l l impair t h e hold-off character is-

t i c s of t he tube.

Two tes t dimen-

f. The external cooling c o i l s f o r the tube cons t i tu te the major

conductors through which current w i l l flow during the pulse r i s e t i m e .

B. PRCUECT DEVELOPMENT ACTIVITIES

I n addi t ion t o supervising and conducting tests f o r the various

subcontracts, as mentioned above, t h i s period has been devoted t o con-

t inued t e s t i n g of conventional igni t rons (primarily Type 6228) t o

assess the va l id i ty of a theory of pulsed ign i t ron operation that has

been developed. To t h i s end w e have placed pa r t i cu la r emphasis on law-

current deionization t i m e measurements i n order t o determine i f the in-

f l e c t i o n point i n the percentage of ionizat ion as a function of current,

as derived from t h i s theory, e x i s t s o r not,

be confirmed, as shown by the p l o t of measured and calculated data i n

Fig. 3.

The calculat ions appear t o

- 21 -

X.

n rn a, k a,

PI 8 v

H

x

- 22 -

XI.

X I . VACUUM SYSTEM

A, MAlK I V CONVERSION

The proposed vacuum system components are in s t a l l ed and successful-

The system w a s l eak checked, l y operating i n the Mark I V vacuum system.

with very f e w leaks discovered.

darn t o 5 X 10

in t e rna l contamination.

t he system.

mm of Hg.

and t h a t a vacuum of t h i s l e v e l can be a t t a ined i n a manifold system.

B. C W O N E N T DESIGN

The high-vacuum manifold w a s pumped -6 mm of Hg, where t h e vacuum held steady because of

The manifold w a s then baked a t 3OO0C t o outgas

The manifold, after baking, reached a pressure of 5 X 1 0 -9 This indicates t ha t t he components w i l l operate successfully

The various components t h a t have been designed were subjected t o

l i f e tests, with sa t i s f ac to ry results.

make t h e components more e f f ic ien t , longer l a s t i n g and cheaper t o f ab r i -

cate.

C. FEASIBILITY STUDIES

Further design i s necessary t o

Several f e a s i b i l i t y s tudies were made t o assess the economics of

t h e various workable systems. These s tudies showed t h a t a manifold

system has economic advantages over an individual pumping system.

study a l s o made c l ea r ce r t a in weaknesses i n a manifold system and where

fu ture development work must be done.

the fu ture research and development program f o r the Vacuum Group.

D. PROBLEMS TO BE RESOLVED

The

The study, i n e f f ec t , l a i d out

1. An automatically operated bakeable ultra-high vacuum valve

must be developed.

2.

be developed.

3.

Larger s ized bakeable valves, up t o 16 inches i n diameter, must

A cheaper means than t h e ion gauge f o r recording vacuum w i t h

t he same accuracy must be worked on.

4. A more e f f i c i en t and cheaper diffusion pump t r a p should be

designed.

5. Outgassing s tudies must be made t o understand b e t t e r t h e

problem of pumping a two-mile system t o ultra-high vacuum.

- 23 -

XI:.

6. An improved vacuum pump to reach ultra-high vacuum levels at high speed must be developed.

7. Further experiments to prove the feasibility of an ultra-high vacuum manifold system should be made.

E. CONCLUSTONS

1, The present components and system concept will work successful- ly for vacua in the mm of Hg range.

2.

designs

3.

Work will have to be continued to provide improved component

Much work has to be done to make the components less costly.

- 24 -

XII. SUPPORT AND ALIGNMENT STUDIES

A. GENERAL

1. Contributions to Mark IV Minor alterations to the accelerator tube support system were made.

This amounted to providing a continuous strut from floor to overhead

member in place of the hook support originally used.

that this was the simplest method of securing the required rigidity.

To assist in locating klystrons, etc., assistance was given in

It was concluded

establishing bench marks on the floor of the Mark IV room that are referenced to the bench marks in the accelerator trench.

2. Trip East

During this period the Perkin-Elmer Corporation (Norwalk, Connecti-

cut), Autometric Corporation (New York, New York), Eastman Kodak Company (Rochester, New York), and Brookhaven National Laboratory (New York)

were visited. Each of these companies presented an alignment proposal. 3. Site Earth Movement Study

To establish the final support and alignment design criterion, an

effort is being made to determine rates of earth movements.

of the two precise elevation surveys, completed 60 days apart, are inconclusive. However, these surveys seem to confirm the geological

findings that the Eocene structures (west end) are less stable than

the Miocene structures (east end).

elevation survey, soon to be started, will be more indicative.

Results

It is hoped that the third precise

M r . 0. S. Reading, who directed the surveying of the AGS machine

at Brookhaven National Laboratory, was asked to consult with Stanford University and ABA at Stanford.

are described in an ABA memo, dated May 3, 1961, entitled, "Ground Measurement Systems-Engineering Geology."

The results of the Stanford meeting

ABA is currently negotiating with a local firm to perform a series of precise horizontal surveys, Both triangulation and trilateration

are to be used. will be achieved in both types of survey.

It is hoped that accuracies to one part in a million

4. Magnetometer Survey Observations have been completed along the entire length of the

- 25 -

XI1 .

site at intervals of eighty feet or less. Maximum variation of the field strength was found to be 160 gamma (1 gamma =

B. SUPPORT

gauss).

Current design philosophy is to support two accelerator tube sec- tions on a substructure. Each substructure is to have an adjustable

support at one end. The other end is to be positioned through being

attached to the following substructure. It is assumed that the earth

movements affecting alignment will be small and realignment will be

infrequent. The adjusting mechanism will be manual; however, provision

will be made f o r converting the mechanism to remote operation.

C. ALIGNMEW

Various alignment methods are under consideration. Which method

or combination of methods will best serve the needs of the project is yet to be decided.

- 26 -

..

XIII.

XIII. CONTROL SYSTEM STUDIES

The general objective of the Instrumentation and Control Group has

been to formulate a design for the instrumentation and control system

for the Project M accelerator. emphasis has been on simplifying the operational concepts and, conse-

quently, the complexity of the control system to be utilized with the

M accelerator. During the last quarter the following objectives were

pur sued

1,

During the past fiscal year the main

Formulation of the operation and maintenance policies and pro-

Associated with cedures that will influence the control system design.

this has been the question of how much relative emphasis is to be placed

on the tolerances of the various machine parameters.

2* Technical feasibility studies of ideas that show promise of

simplifying the complexity of the control system.

Conceptual design of the control system for the test cells and 3. the test accelerator.

4. In addition, one of the staff members visited the following labora-

tories: Brookhaven, CERN, Orsay, Hamburg, Vickers Research Limited, and

Harwell to study the present status of high-energy machines in the

United States and Europe. A trip report is in preparation.

A,

Budgetary estimates for Fiscal Years 1962 and 1963.

GENERAL STUDIES DURING THE LAST QIIARTER

1. Beam Control and Maintenance Two of the problems to be dealt with during beam operation are: a. The control of the energy and beam intensity of the analysed

beam current, which is subject to continuous variations resulting from changes in accelerator temperature, frequency, klystron voltage varia-

tions, rf phase, etc.

b.

Parameter changes and loss of klystron power will produce energy

The continuance of operation in the event of component failures.

and phase variations in the acceleration, It is proposed to compensate

for these variations by feedback to the phase control system and to the applied voltage of the klystrons.

either the drive system or the buncher, whereas the most promising The phase control may be handled by

- 27 -

XIII.

scheme f o r control l ing klystron voltage seems t o be by the DeQ'ing

c i r c u i t s i n t h e modulator power supplies. That is, it should be possi-

b le t o remotely control t h e reference voltage t o these c i r c u i t s , which

w i l l change the l e v e l of t h e klystron beam voltage and, consequently,

t h e r f output,

The input information f o r t h e phase and energy control systems may

be derived from a knowledge of t he in t ens i ty of t he analysed beam cur-

ren t as a function of t he output energy. This information can be ob-

ta ined from monitors sui tably placed across the energy defining s l i ts

i n the beam extract ion area,

The most frequent source of component f a i l u r e w i l l be t he l o s s of

rf power from a klystron.

f o r various components, more than 90$ of a l l expected f a i l u r e s w i l l be

from klystron f a i lu re s .

be recovered by the 32 tubes of one power supply, t he voltage adjustment

necessary t o compensate f o r t h i s w i l l be of t he order of 3%. if only 3% reserve voltage i s avai lable , t he replacement of t he klystron

Based on an estimated average f a i l u r e r a t e

I f t h e lo s s of output from one klystron has t o

Clearly,

must be completed before

yeserve per power supply

DeQ'ing c i r c u i t s must be

machine. The pa r t i cu la r

t he next f a i l u r e i s expected, more voltage

must be provided, o r voltage control of t h e

extended over more than one sector of t he

procedure adopted depends on t h e maintenance

policy chosen f o r t he klystrons. In any event, t he solut ion chosen

should be tha t which of fers t he grea tes t probabi l i ty for maximizing the

b eam- on time

2 . Technical Considerations and Costs Applicable t o Data Communicat ions

A review of technical considerations and costs applicable t o t h e

data communication system has been made. An analysis of costs f o r

accelerator control has been prepared and w i l l be published next quar-

t e r as an in t e rna l memorandum. This report w i l l include a review of

per t inent technical fac tors and cost considerations f o r t h e various

types of control s ignals , The breakdown i n cost of handling the

presently an t ic ipa ted volume of s ignals by various means has been

studied a l so ,

- 28 -

XIII.

3. Feasibility Studies

Analytical calculations are being made to check the feasibility of

injecting into the accelerator at an angle.

prime question of the tolerances imposed upon any magnetic or electro- static injection system that may be used for this purpose, Also, there

is the technical question of the amount of debunching that occurs as particles pass through the system.

of the two systems considered, one system has approximately 100 times less debunching effect than the other for a one-percent energy spectrum,

We are now in the process of calculating the necessary alignment toler-

ances demanded of the system.

Associated with this is the

It has been possible to show that,

Another feasibility study in process is a calculation to determine

the strength and the number of quadrupole "field" lenses that may be

required for steering the electron beam down the accelerator. .This study is intimately related to the alignment procedure that will be

used for the accelerator. We are experimenting with various alignment procedures to see what effect each of these will have on the over-all

cost of the beam steering system. the Support and Alignment Group as soon as satisfactory results have

been obtained.

Bo INSTRUMENTATICIN AND CONTROL SIGNALS

A preliminary report will be made to

During the last quarter a list of all control and monitoring sig-

nals was completed. Block diagrams of the possible instrumentation sys- tem for these signals have been made. These diagrams are now undergoing

a critical review and modifications. It is intended that a document

containing the block diagrams will serve as an outline of the basic instrumentation requirements of the accelerator.

In addition, the Instrumentation and Control Group has been ac-

tively designing the consoles for the klystron and modulator test cells to be installed in the first building on the project site. The con-

ceptual design of the consoles is completed and the engineering details

are progressing.

Each console will contain a basic complement of instruments and

controls consisting of cabinets, an oscilloscope, rf power meters and certain interlock connections to complete the basic console. The

- 29 -

XIII.

modulator control paneling, rf driver system, vacuum monitors and con-

trols, 'water controls, flow meters, and temperature monitors will be

provided by the other component groups and not by the Instrumentation

and Control Group. However, the final interconnections o f the system

will be made by the Instrunentation and Control Group.

- 30 -

..

XIV.

XIV. GENENU RF STUDIES

A. CONSTANT -GRADIENT ACC-T OR STRUCTURE 1, Measurement of Quality Factor Q as a Function of z No conclusions can yet be drawn as to the precise nature of the

I

variation of Q with distance along the accelerator section. The

effect of surface roughness on the Q has been shown to be considerable,

and electropolishing has resulted in a significant increase in the value of this parameter. Measurement difficulties continue, however, and these are being investigated in detail.

2. Coupler Design

Two couplers have been designed and built and will be matched into the input and output ends of a constant-gradient section.

3. Measurement of the Fundamental Space Harmonic Amplitude A series of experiments has been conducted to determine the influ-

The ence of the resonant frequency on the space harmonic amplitude.

results are presently being analyzed.

lating the space harmonic content from the experimental results has been

derived and will be given in detail in a separate memorandum.

El. COKKXLI DISK STRUCTURE

A more accurate method of calcu-

Modifications of the disc to obtain the correct operating parame-

ters are still being undertaken, after which an anlysis of the signifi-

cant properties will be mde.

- 31 -

XV. RESEARCH AREA DESIGN AND RELATED PROBLEMS

A. RADIATION SHIELDING

1, Reports Issued During t h e Past Quarter

a. H. C. DeStaebler, Jr., "Review of Transverse Shielding Require- ments f o r t he Stanford Two-Mile Accelerator," M Report No. 262, Stanford University, April 1961.

This report shows that a transverse shielding thickness of 35 f t of

ear th (or equivalent) , a s used i n the o r ig ina l Stanford proposal, i s

probably sa t i s fac tory .

hundred Mev neutrons determine the shielding thickness.. The cross sec-

t ions a r e f a i r l y well-known i n t h i s energy range.

t y i n t h e calculat ion of t he transverse thickness concerns the propaga-

t i o n through the atmosphere of t h e neutrons and secondary radiat ions

which come out of t he shield. An exact calculat ion of t h i s process i s

very complicated and has been undertaken by a computer group a t Cak

Ridge,

apprecfable uncertaint ies concern t h e energy spectrum of neutrons coming

The production and at tenuat ion of several

The biggest uncertain-

We a r e t ry ing t o make an improved simple estimate. Two other

out of t h e sh ie ld and the b io logica l hazard of neutrons with energies

above 30 Mev f o r which there a r e no published data.

b. H. DeStaebler, Jr, , "Radiation Levels Inside t h e Project M Accelerator Tunnel," M Report No, 263, Stanford University, m y 1961,

This report estimates the instantaneous radiat ion l eve l s inside the

shielding when t h e machine i s running.

those from induced, res idual ac t iv i ty . Under average operating condi-

t i ons and a t a distance of 5 ft from t h e beam pipe, t he neutron f lux i s 5 2 5 x 10 8 2 2 X 10 Mev/cm -see.

f a c t o r i l y (within a f ac to r of 3) with experimental measurements made

with f i l m badges.

These l eve l s a r e much higher than

n/cm -see, and the photon-electron energy f l u x i s

A s i m i l a r calculat ion f o r Mark 111 agreed satis-

c , J. J. Muray, "Muon Yields from Pion Decay and Electromagnetic Pair Production," M Report No , 267, Stanford University, ~ a y 1961.

This report shows t h a t the rad ia t ion hazard of muons penetrating the

transverse shielding along the machine i s negl igible when compared with

the neutron problem, However, t he f lux of muons i n the forward direct ion

can be la rge and i s hard t o stop.

account of t h i s hazard.

The t a rge t a rea design must take

- 32 -

1

2. Current Investigations

a, The radiation level arising from residual radioactivity induced

in various materials struck by a high-energy electron beam.

lations will be compared with experiments performed at the Mark 111 accelerator,

The calcu-

b. Design of ducts and tunnels through the transverse shielding.

There is appreciable information on ducts through reactors, but only

scanty information on ducts through shields for high-energy accelerators.

At present, the proposed ducts for the waveguide feeds (about 2 ft in

dfameter not pointing directly at the beam pipe) seem all right.

c. The efficacy of collimators placed inside the accelerating

structure to scrape off electrons at the edge of the beam before they

strike the loading disks.

of the sources of radiation even though the total source strength remains

the same. This would simplify greatly almost every radiation problem associated with the accelerator itself,

The goal is to limit the spatial distribution

We have discussed with the nuclear emulsion group at UCRL (Livermore)

possible experiments to be done at Brookhaven National Laboratory or

CERN to investigate the attenuation of high-energy (25 Bev) beams in large depth (20-ft iron) of shielding. B. ACCELERATOR HEITING

Heating of the disk-loaded accelerator structure is caused by absorption of the electron beam energy, A calculation is being made

which will take account of the details of shower development, energy

loss and accelerator structure geometry. General calculations on 13 heating are discussed by S. Penner.

C. BEAM HANDLING SYSTEMS The length and characteristics of the magnetic deflection systems

are being re-evaluated.

magnetic deflection system with a 2" aperture can produce a displacement

of about 1 ft in a 90-ft distance, using an energy transfer system with

a power-handling capacity of about 1 megawatt,

In particular, it has been shown that a pulsed

For a simple one-direction deflection the displacement D is 3 1/2 related to the power P and distance L by D e (PI, )

13. S, Penner, "Note on Power Dissipation from Collimators and Targets for High-Energy, High-Power Electron Beams," M Report No. 200-6, Stanford University, July 26, 1960.

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XVI .

XVI. PLANT EXGINEERING ACTIVITIES

The preliminary s i t e plan f o r t he Laboratory i s shown on the

following page.

Atomic Energy Commission, t he Trustees of Stanford University, and t h e

Staff of Project M. and it i s now possible t o proceed with f i n a l design drawing.

This layout has been submitted t o the United S ta tes

The approval of t h i s s i t e plan has been granted

The prelirninarn design of t he first building on the s i t e , t h e T e s t

Laboratory Building, has been submitted for approval. It i s ant ic ipated

t h a t construction work on t h i s building may start i n the l a t e f a l l of

1961, and be completed i n mid-summer, 1962.

Work on the master plan f o r t he construction of t he s i t e , buildings

and u t i l i t i e s i s proceeding.

following construction problems:

Engineering s tudies have been made on the

1, S i t e S t a b i l i t y

a, Earth s t r a i n

b Subs idenc e

c Seasonal movements

Cross Section f o r Accelerator and Klystron Gallery Structures

Methods of Close Temperature Control i n Large Cooling Systems

2.

3. Construction of buildings w i l l s tart with t h e re lease of F isca l

Year 1962 funds and a l l building construction w i l l be completed by

Fisca l Year 1966,

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w

XVII .

XVII. AC PWER SYSTEM

Extensive load requirement surveys were made during this quarter as

The a joint Stanford-ABA effort to determine the project power demands.

results of the analysis of these demands has been compiled by ABA.

Preparation of electrical information for the preliminary proposal

The following on the Test Laboratory was completed during this period.

tables give a brief summary of the building's electrical system.

TEST LABORATCIRY: CONNECTED LOAD REQUIREMENTS

Building Service Cranes 44 kva Air conditioning, heating and ventilating 42 kva Building lighting 164 kva Convenience outlets 100 kva

Subt ot a1 350 kva Klystron Fabrication, Assembly, Process and Test

Modulator power supplies 2,400 kva Modulator auxiliaries, vacuum, control, etc. 1,172 kva Tube Shop wing 1,021 kva

Fabrication and assembly bays 1,512 kva Test auxiliaries, compress., control 110 kva

6,215 kva Sub t ot a1

Test Accelerator Housing Service

Lighting and convenience outlets Test Accelerator

Modulator power supplies

Modulator auxiliaries, control, etc. Vacuum

65 kva

Injection and beam analysis 178 kva 900 kva Sub t ot a1

TOTAL CONNECTED LOAD 7,530

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X V I I .

TABU I1

TEST LABORATCRY: ILLUMINATIClN LEVELS

Assembly bay, fabr ica t ion bay, klystron t e s t ,

furnace, tube fabr ica t ion , instruments,

e lectronics , chemistry, laboratory, o f f ice , e t c . 100-f oot candles

2. Maintenance 50-f oot candles

3. Heat exchanger area, mechanical equipment,

1.

s to re s 30-foot candles

Primary power service f o r t he building i s t o be 12 k i lovol t s ,

3 phase, 60 cycle, delivered underground i n polyethylene-insulated,

single-conductor cables.

t h e main bui lding s h e l l .

480 vol t s , 3 phase, 3 wire, with r equ i s i t e quant i t ies of 277 vo l t ,

&-wire service f o r l i gh t ing c i r c u i t s .

equipment i s t o be provided on unit substat ions.

The substat ion i s t o be located external t o

Power i s t o be provided t o the bui lding a t

Watt-hour and demand metering

Many of t he loads a r e of such l a rge s i ze t h a t they must be fed

d i r e c t l y from the substation.

have b u i l t - i n control panels.

Most of t he equipment being t e s t e d w i l l

Low voltage 120/208 vol t s , 3 phase, &-wire wye service is t o be

obtained from dry-type transformers.

Ehergency power f o r c r i t i c a l c i r c u i t s i s t o be supplied a t 480 vo l t s by an engine-driven generator.

Fluorescent l i g h t i n g f i x t u r e s a r e t o be 277-volt high-power f ac to r

type. Incandescent f i x t u r e s a r e t o be 120 vol t s .

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XVIII.

XVIII. COOLING-WATER SYSTEM

A, TWO-MILE ACCELERATOR

The master plan for the water system has been virtually completed, except for the location of the water storage tank. tained from the Hetch-Hetchy (City of San Francisco water system) aque-

duct which runs by the northeast corner of the site, will be necessary to provide adequate distribution and fire protection

pressure. The water will be distributed throughout the plant in a normal fashion to supply buildings with domestic water and fire protec-

tion, and to provide cooling-water system make-up.

Water will be ob-

A pumping plant

Two large cooling-tower stations will serve the plant, one located about half'way along the two-mile accelerator to serve the Klystron

Gallery and Accelerator Housing, and the other located near the end

stations to serve the end station area yard, the Test Accelerator

Building, and any other needs in the general area of these structures,

In the case of the two-mile accelerator, cooling-tower water will

be distributed to fifteen (15) identical heat-exchanger installations spaced about 640 feet apart along the length of the accelerator. these points the demineralized, low-conductivity, cooling-water circuits

serving the klystrons, modulators, etc., will give up heat to the

cooling-tower water and be pumped back to the electronic equipment. This arrangement was decided upon on the basis of ABA Report, "Heat

Transfer System Study" ( ABA- 3 ) .

At

In the case of the end station area, cooling-tower water will be

distributed to heat-exchanger installations located adjacent to the

major cooling load centers, where the exchangers will pick up the heat load f rom the law-conductivity cooling-water systems.

A study has been made by entitled "Accelerator Tube Deminer-

alized Water System Instrumentation and Control Study" (ABA-5). The study examines the various alternatives open for controlling the acceler-

ator tube water temperature to f 1 / 2 O F ,

system was recommended and will be installed on the Test Accelerator

for testing,

A solid-state electronics

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XVIII.

The cooling-water system f o r t he Test Laboratory Building and Test

Accelerator has been car r ied through the preliminary design stage.

B. MARK I V

The cooling-water system for t h e revised Mark I V machine has been

completely in s t a l l ed . This includes a l l new copper piping, provision

f o r using demineralized water i n t h e closed c i r c u i t system, and emer-

gency cooling water f o r t he vacuum pumps. A pneumatic control system

w a s included t o provide k 112 F control of t h e accelerator tube cooling

water.

accelerator jacket temperature and flow water over a wide range.

C. PRCXTECT M BUILDING

0

It w i l l be possible t o remotely and automatically control t he

Good qual i ty w a t e r has been provided for equipment cooling purposes

This through a connection t o t h e Hetch-Hetchy system on E l Camino Real.

water w a s d i s t r ibu ted throughout t h e building t o t es t stands,

D. FESEARCHANDDEVELOPMENT

A method of providing uniform cooling of t he accelerator tube has

been proposed, wherein water would be boi led i n the acce lera tor tube

water jacket under a vacuum corresponding t o the vapor pressure of t he

w a t e r a t t h e desired temperature.

next s i x months i n connection w i t h experimental work on the design of a

su i tab le water jacket .

This method w i l l be t e s t e d out i n t h e

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XIX. HEATING AND VENTILATING

Preliminary design of the heating and ventilating system for the Test Laboratory Building was completed during the last quarter.

A study was made by ABA concerning air-conditioning practice in the Pa10 Alto area and its application to Project M (ABA-7).

Some information has been gathered relative to the possible genera- tion of toxic and/or corrosive gases by an electron beam exposed to air.

Further information must be obtained, relative to the quantities of such gases that might be generated, so that firm conclusions may be made as

to the possible hazard. At this time it is planned that accelerator

housings will be sealed during beam operation (no ventilation), and for

a sufficient decay period thereafter, prior to ventilating for personnel

access.

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C . T