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Experimental studies and analysis of the vertical emittance growth in the ATF extraction line in 2007-2008

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HAL Id: in2p3-00424391

http://hal.in2p3.fr/in2p3-00424391

Submitted on 15 Oct 2009

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Experimental studies and analysis of the vertical

emittance growth in the ATF extraction line in

2007-2008

M. Alabau Pons, A. Faus-Golfe, P. Bambade, S. Kuroda, G. White, M.

Woodley, A. Scarfe

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Experimental Studies and Analysis of the Vertical Emittance

Growth in the ATF Extraction Line in 2007-2008

M. Alabau Pons

1,2

, A. Faus-Golfe

1

, P. Bambade

2,3

S. Kuroda

3

, G. White

4

, M. Woodley

4

, A. Scarfe

5

1) IFIC (CSIC-UV), Valencia, Spain

2) LAL, Univ. Paris-Sud, CNRS/IN2P3, Orsay, France

3) KEK, Tsukuba, Japan

4) SLAC, CA, USA

5) Cockcroft Institute, Univ Manchester, UK

Abstract

The Extraction Line (EXT) of the Accelerator Test Facility (ATF) at KEK will transport

the electron beam from the ATF Damping Ring (DR) to the future ATF2 Final Focus

beam line. Since several years, the vertical beam emittance measured in the EXT line is

significantly larger than that measured in the DR itself, and there are observations that the

growth increases with beam intensity. A possible contribution is the non-linearity in the

magnetic fields experienced by the beam when passing off-axis through several magnets

shared by the DR and the EXT beam line in the initial part of the extraction process.

Tracking simulations including non-linear field errors in these magnets predict significant

emittance growth when the beam is displaced vertically with respect to the nominal

trajectory. An experimental program has been carried out during 2007-2008 to study the

relation between the extraction trajectory and the anomalous emittance growth. This note

reports on the results of this program.

1

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7 7.5 8 8.5 9 9.5 10 10.5 11 77000 77200 77400 77600 77800 78000 78200 σy,OTR (channels) time (s) 6 7 8 9 10 11 12 13 14 77000 77200 77400 77600 77800 78000 78200 σy,XSR ( µ m) time (s) 7 7.5 8 8.5 9 9.5 10 10.5 11 77000 77200 77400 77600 77800 78000 78200 σy,OTR (channels) time (s) 6 7 8 9 10 11 12 13 14 77000 77200 77400 77600 77800 78000 78200 σy,XSR ( µ m) time (s) 12 12.5 13 13.5 14 14.5 15 15.5 16 16.5 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 σy,OTR ( µ m)

abs(y bump amplitude) (mm)

6 7 8 9 10 11 12 13 14 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 σy,XSR ( µ m)

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1.3 1.4 1.5 1.6 1.7 1.8 1.9 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 σy,OTR /σy,XSR

abs(y bump amplitude) (mm) measurements polynomial fit 1 1.5 2 2.5 3 0 0.2 0.4 0.6 0.8 1 Normalised σy,OTR /σy,XSR

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0

0.2

0.4

0.6

0.8

1

1.2

1.4

21500

23500

25500

27500

Beam Intensity (10

10

e

-

/pulse)

time (s)

Measurement 1

Measurement 2

Measurement 3

25 26 27 28 29 30 31 32 33 34 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 σy,OTR ( µ m)

absolute y bump amplitude (mm) Measurement 1 Measurement 2 Measurement 3 8 9 10 11 12 13 14 15 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 σy,XSR ( µ m)

absolute y bump amplitude (mm) Measurement 1

Measurement 2

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25 26 27 28 29 30 31 32 33 34 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 σy,OTR ( µ m)

abs(y bump amplitude) (mm)

8 9 10 11 12 13 14 15 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 σy,XSR ( µ m)

abs(y bump amplitude) (mm)

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5 10 15 20 25 30 -1 -0.5 0 0.5 1 σy,OTR ( µ m) y bump amplitude (mm) 5 10 15 20 25 30 -1 -0.5 0 0.5 1 σy,XSR ( µ m) y bump amplitude (mm) 0 10 20 30 40 50 60 70 80 -1 -0.5 0 0.5 1 σy,OTR ( µ m) y bump amplitude in QM7 (mm) εx=2.2 nm, εy=23 pm, W/O coupling εx=2.2 nm, εy=23 pm, With coupling Measurements 28th MAY’08 0 50 100 150 200 250 -1 -0.5 0 0.5 1 εy,OTR (pm rad) y bump amplitude in QM7 (mm) εx= 2.2 nm, εy=23 pm, W/O coupling εx=2.2 nm, εy=23 pm, With coupling

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