02.11.1

A plan of ATF Final Focus Test BeamLine (A-FFTB)

1. Introduction

2. Optics

3. Summary

02.11.1

ACCELERATOR TEST FACILITY FOR LC

Jan.14, 1998 120m

50.

4m

16.

8m

1.54 GeV Damping ring

1.54GeV S-band LINACDamped cavities Wiggler magnets Positron source

Beam diagnostic system (EXT)

Wiggler magnetsWater cooling & Air condition facility

Water cooling & Air condition facility

ModulatorsKlystrons

RF gun

DC power supply for modulator

Polarized electron source

714MHz RF source

Magnet power supply

53.4m

27.

6m

13.8m

Aug.'93

Nov.'95

Jan.'97

Nov.'97

02.11.1

50.4m

L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 Lec2 L13 L14 L15 L16Lec1

120m

X-band Section

Bunch Compressor

1.54 GeV S-band Linac

1.54 GeVDamping RingControl Room

Final Focus

ATF-II

(ATF2)(ATF1)

(30psec to 3psec)

02.11.1

KEK is discussing ATF-II as next R&D for LC’s.Proposal of ATF-II will be obtained within two months.

*High Gradient beam acceleration with compact X-bandSystem. (ATF1)

*Test of F.F. Optics (Proof of Principle Experiment). (ATF2)Stabilization, FD to realize 50nm even if 1.3GeV.

Shigeru Kuroda, K.Kubo, T.Okugi, T.Tauchi and me (J.Urakawa)

T.Tauchi : Leader of ATF2

02.11.1

ATF1:Simplest 2 single-mode DLDSATF1:Simplest 2 single-mode DLDSand high gradient acceleration withand high gradient acceleration with1.3GeV low 1.3GeV low emittance emittance beambeam

l DLDS Experiment with Two 75MW Klystronsl High Gradient Acceleration with 1.3GeV beam

ATF1 has higher priolity. This is not related to my talk.So, I will explain ATF2 for this workshop.

02.11.1

35m

P.Raimondi and A.Seryi Lattice: Test of New Optics

Scaling (FFTB and ATF2) by only PhysicalEmittance

60nm •46

1.543 ¥10-6

3 ¥10-8 = 33nm!

IP

From ATF

02.11.1

Ds * = xds 0*

d =Dpp

s0* :linear optics beam size

Sexta in Dispersion region for chromaticity correction.-I: Nonlinear Effect is cancelled.

02.11.1

P.Raimondi and A.Seryi (New FF Lattice)~1600m is reduced ~500m.

2nd order geometric aberration is cancelled by SF1 and SD1.

02.11.1

MP =

F 0 0 0F2 1 1/ F 0 00 0 F 00 0 F4 3 1/ F

Ê

Ë

Á Á Á

ˆ

¯

˜ ˜ ˜

QM =

D 0 0 0D2 1 1/ D 0 00 0 D 00 0 D4 3 1/ D

Ê

Ë

Á Á Á

ˆ

¯

˜ ˜ ˜

K2SF1 = -F3K2SF 2

K2SD1 = -D3K2SD2

Remain 3rd order geometric aberration.

02.11.1

Thin lens approximation:

K2SF1 = -F3K2SF 2

K2SD1 = -D3K2SD2

U3444 µ N3 42 Q1 2 N2 3Q3 4 + N3 4Q4 4( )2

U1244 = U3224 µQ1 2N3 42 NQ( )1 2

2 + Q1 2N1 22 NQ( )3 4

2 - 4Q3 4N1 2N3 4 NQ( )1 2 NQ( )3 4

1,2,3 and 4 correspond to x, px, y and py

U1244 = U3224 = 0U3444

By final quads: make small.

02.11.1

Computer Program SAD:(http://acc-physics.kek.jp/SAD/sad.html1.54GeV, 3x10-6, 3X10-8, Dp/p=0.1%(Gaussian Distribution)*Large Geometric Aberration due to large physical emittance*Smaller nonlinear effect due to 0.1% energy spreadComparing LC’s design.Required Condition:

L* = 2m(IP - QD), (QF - SD2) = 2m(SF2 - QF) = (SD2 - QD) = 0.3m

KQD = -0.67m-1, KQF = 0.31m-1

U3444 = 9.57 (not minimum but optimum choice considering x)

P-Lattice and Q-Lattice are identical. F=-1.12 and D=-0.893

KQuad £ 0.2m-1

02.11.1

SF1 SD1 SF2 SD2

IP

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Matching atMatching atIP:IP:aaxx==aayy=0,=0,bbxx=0.01m,=0.01m,bbyy=100=100mmm,m,hhxx=0 for=0 fordd=-0.2%,-0.1%,0%,0.1% and 0.2%=-0.2%,-0.1%,0%,0.1% and 0.2%

DP -0.2% -0.1% 0% 0.1% 0.2%

ax -0.089 -0.019 0.008 -0.010 -0.074

bx[cm] 1.01 1.01 1.01 1.02 1.03

ay -0.063 0.003 0.007 -0.024 -0.058

by[mm] 102 102 101 101 101

hy[mm] -110 -20 12 -28 -153

K2SF 2 = -1.2m -2 , K2SD2 = 3.5m-2

02.11.1

Accidentally, the dispersion at the final sextupole magnets isAlmost zero. This means the chromatic correction is done byThe sextupole pair upstream and downstream sexta play theRole of the geometric aberration cancellation.--->h=h’=0

Tracking Simulation: 1000 particles, No Errorsx*=3.42mm, sy*=36.8nmError : 100 seedsDsrot=0.1mrad, Dsz=500mm, Dsx=100mm, Dsy=50mm,DsDB/B=0.01% one s cut distributionAfter correction with ideal BPM and spot size monitor,Orbit Correction, Skew Correction, Position Correction ofSexta and FD.sy*=47nm (90% C.L.)If Dsrot=0.02mrad, Dsz=50mm, Dsx=30mm, Dsy=30mm,sy*= 37nm??

02.11.1

Tuning Method1. Orbit Correction with ideal BPM’s (15 Quads), Longitudinal Movement of 2 Final Quads and 4 Sexta on Movable girders with ideal beam size monitor at IP.2. (Orbit + Dispersion at 2 sexta near IP and IP): MinimizeFQ, Sexta on Movable girder: tuning3. 1-2 tuning : 4 times

First dispersion correction requires strong steerings. So, we donot correct the dispersion due to error of quad-rollBy steering magnets at first.

From ATF Alignment experience, Initial alignment of roll and pitch are +/-0.02mrad is possible by peak-to-peak.However, the diffusion of the alignment is fast and 0.15mradpeak-to-peak is diffused after about half year.

02.11.1

50nm

02.11.1

Shigeru Kuroda asked me to say following “Words”;“これは、とっても難しい ” It’s so challenging becauseof low energy 1.5GeV.This is preliminary results. However, proposal for ATF-IIwill be completed by Tauchi (Group leader of ATF-FFTB).

SummaryIt is very important to test experimentally the principle of thenew final system. The beam size is expected as sx=3.4mmand sy=37nm.R&D for some hardware is required.