Kentech Instruments Ltd. Slow Sweep Unit STREAK CAMERA · Sweep unit timing switch (KT106/modified...

Kentech Instruments Ltd., Unit 9, Hall Farm Workshops, South Moreton, Didcot, Oxon, OX11 9AG, England.

3rd. March 20041

Kentech Instruments Ltd.,

Unit 9, Hall Farm Workshops, South Moreton, Didcot, Oxon, OX11 9AG, U.K.

Tel: 01235 510 748 Fax: 01235 510 722

International tel: (44) 1235 510 748 International fax: (44)1235 510 722

E-mail [email protected]

Kentech Instruments Ltd.

Slow Sweep UnitSTREAK CAMERA

3rd. March 2004

PLEASE READ THIS MANUAL CAREFULLY BEFORE USING

THE SWEEP UNIT.

Serial Number

2


3rd. March 2004

DISCLAIMER

This equipment contains high voltage power supplies. Although the current supply capacity is small, careless use

could result in electric shock. It is assumed that this highly specialised equipment will only be used by qualified

personnel.

Kentech Instruments Ltd. accept no responsibility for any electric shock or injury arising from use or misuse of

this equipment. It is the responsibility of the user to exercise care and common sense with this highly versatile

equipment.


3rd. March 20043

Figure Captions

Figure 1 The ramp speeds 6

Figure 2 Positive slow ramp generator 7

Figure 3 Negative slow ramp generator 8

Figure 4 Sweep unit, block diagram 9

Figure 5 Sweep unit timing switch (KT106/modified rates) 10

Figure 6 Sweep unit Trigger board (KT101) 11

Figure 7 Slow ramp board showing adjusters 12

Figure 8 Slow ramp layout 13

Contents

DISCLAIMER 2

1 INTRODUCTION 4

1.1 SPECIFICATIONS 4

2 CIRCUIT DESCRIPTIONS 4

3 DATA SHEETS 5

3.1 SWEEP CIRCUIT 5

3.2 TRIGGER DELAYS 5

3.3 BIAS VOLTAGES 5

4


3rd. March 2004

1 INTRODUCTION

This manual describes the operation and use of the Kentech Sweep unit. The manual gives the mechanical and

electrical specifications and describes the setting up procedure.

1.1 SPECIFICATIONS

Trigger delay sweep unit ~40ns on the fastest setting, see timing graphs

Number of sweep speeds four

Supply Universal

Sweep Trigger input Normally 10volts, rising in

1ns for minimum delay

8 Volts and 6ns fwhm is just enough to trigger the

unit, but good jitter will require a larger signal.

Sweep hold off time approximately 20ms

Repetition rate 10Hz.

2 CIRCUIT DESCRIPTIONS

The sweep circuit has two separate ramp generators one for the two faster speeds and a second for the two slower ones.

The fast unit is based on two high voltage avalanche step generators unique to Kentech. These two generators provide balanced

steps of amplitude +/- 1.5kV into 100W loads, with a rise time of <1ns. These generators are fed into the sweep leads via 50Wreverse terminating resistors, which reduces the amplitude to > 0.75kV. When this edge reaches the open circuit end at the

sweep plates it doubles up to > 1.5kV. The reverse pulse is absorbed by the reverse terminating resistors. A block diagram of

the unit is shown in figure�5.

Different sweep rates are obtained by the switchable pulse forming LCR network and selected by the two most clockwise

positions of the sweep rate switch (see figure�6). The sweep leads form part of this network and their length must therefore

not be changed.

For the two slower speeds a FET based ramp generator using a Miller integrator is used. This is switched to directly by

the sweep speed selector. The four sweep speeds are selected with the speed selector which switches resistors in the Miller

integrator network. This type of ramp generator is more linear than an avalanche unit and so it is unnecessary to achieve such

high voltages. A result is that the start position has to be closer to the screen edge than the avalanche unit.

A further function of the sweep unit is to provide the required bias voltages to define the start of the sweep (see figure�8).

There are three positions ,”FOCUS”, ”SYNCH” and “OPERATE”. In Focus mode the trigger is inhibited and the bias voltages

set to zero. In Synch. mode the trigger is enabled and the bias voltages are set by the bottom preset on the rear panel. A value

should be chosen that puts the unswept image just on the screen edge. In operate mode the trigger is enabled and the bias

is set by a preset on the rear panel, one for each sweep speed. These have been factory set to the position that ensures optimum

linearity and lack of flyback onto the screen due to oscillations in the ramp generator circuit.

The sweep unit supplies a monitor output pulse which may be used for synchronisation.


3rd. March 20045

3 DATA SHEETS

3.1 SWEEP CIRCUIT

This sweep circuit has been set up for non standard sweep rates.

Sweep speeds, nominal.

Speed 1 20 V/ns

Speed 2 40 V/ns

Speed 3 76.3 V/ns

Speed 4 256.5 V/ns

3.2 TRIGGER DELAYS

The time between a fast trigger signal arriving at the trigger input of the sweep generator and the ramp voltage

reaching the voltage which corresponds to screen centre is given below. Further allowance needs to be made for the

time of flight of x-rays from the target to the cathode, for the flight time of photoelectrons from the cathode to the sweep

plates and to any extra cabling between the sweep plates and the leads provided. These figures should be use as a guide

only. They are only valid at the factory set bias settings.

Unit 1

Sweep 1 54.8ns

Sweep 2 46.8ns

Sweep 3 43ns

Sweep 4 39.6ns

For Unit 2 subtract 1ns from the above

For Unit 3 subtract 3ns from the above

3.3 BIAS VOLTAGES

Bias SYNCH user to setfor a tube with a round screen and a deflection requirement of ± 407 volts full

screen we suggest a bias of around ±150 volts.

Bias OPERATE

Sweep Speed 1 300 volts




With these settings the trigger delays above correspond to the time for the ramp to reach the bias voltage, i.e.

screen centre.

6


3rd. March 2004

Figure 1 The ramp speeds

Sweep speeds 3 and 4

76.3 and 256.5 V/ns

218V/div, 5ns/div

The steps and oscillations are due to the reflections round the 2

meters of cabling.

It is important to keep the bias low enough that the oscillation on

sweep speed 1 does not retrace the screen.

Sweep speeds 3 and 4

76.3 and 256.5 V/ns

436V/div, 5ns/div

Sweep speed 2

40 V/ns

100V/div, 5ns/div

Sweep speed 1

20 V/ns

100V/div, 5ns/div

Wobbles are due to transit times around

the 2 meters of cable.

Sweep speed 1

ramp balance

Sweep speed 2

ramp balance


3rd. March 20047

33

M

VR

68

sho

rt c

ircu

it R

9 a

nd

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om

itte

do

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om

itte

d

Figu

re 2

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slo

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amp

gen

erat

or

8


3rd. March 2004

Figure 3

Negative slo

w ram

p gen

erator

0R

omitted

omitted


3rd. March 20049

Figu

re 4

Swee

p u

nit

, blo

ck d

iagr

am

Tri

gger

Inpu

t

2 am

p

-1kV

+1k V

Bia

sSw

itch

5 in

vert

ors

+ve

Ste

pG

ener

ator

KT

111/

P

-ve

Step

Gen

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or

KT

111/

N

Bal

ance

Mon

itor

Out

put

+2.

5kV

-2.5

kV

500

volts

L N

IEC

filte

r

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utpu

ts

Tim

ing

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KT

106

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olt

univ

ersa

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supp

ly

Slow

Ram

pge

nera

tors

±710 for

sw

eeps 5

& 6

±400 for

sw

eeps 1

,2,3

,4

+1.

5kV

& 6

0 V

olts

trig

ger

coun

ter

1,3,

5,8,

10,1

5co

unte

r pr

eset

sw

itch

Tri

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and

Mon

itor

KT

101

10


3rd. March 2004

Figure 5

Sweep

un

it timin

g switch

(KT

106/mo

dified

rates)

0.27µH220

47

0.68µH0.27µH

4722

INO

UT

fromavalanche

stackto sw

eepoutput

All capacitors approx 8pf , form

edfrom

double sided pcb 15mm

by20m

m

Slow ram

pG

enerator4 speeds only

12 volts

activate HT

toavalanche stacks

activate HT

to Slowram

p generator

Select slow

sweep bias

voltage

Select fast sweep bias

voltage


3rd. March 200411

Figu

re 6

Swee

p u

nit

Tri

gger

bo

ard

(K

T10

1)

Mon

itor 22

0

100

100

1n

100V

200V

200V

100p

F

1n

10n

+50

0V

1k2

15V

100

10k

100

* *

100

1n

1n 1n

Tri

gger

Inp

ut O

utpu

ts to

Fas

t Sw

eep

Boa

rds

Sw

eep

bala

nce

* S

elec

ted

Tri

gger

Tra

nsis

tors

To

slow

ram

p bo

ard

160V

160V1k 1k

Pot r

emov

edan

d sh

orte

d

1n

12


3rd. March 2004

Figure 7

Slow

ramp

board

sho

win

g adju

sters


3rd. March 200413

Figu

re 8

Slo

w r

amp

layo

ut

Kentech Instruments Ltd. Slow Sweep Unit STREAK CAMERA · Sweep unit timing switch (KT106/modified...

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Transcript of Kentech Instruments Ltd. Slow Sweep Unit STREAK CAMERA · Sweep unit timing switch (KT106/modified...