Holger Schlarb DESY 22607 Hamburg · 09.11.2004 Holger Schlarb, DESY 8 " ˙ • measurement in...

09.11.2004 Holger Schlarb, DESY 1

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Holger SchlarbDESY

22607 Hamburg

• Injector run: Feb 04 – Jun 04• Linac commissioning: Sep 04 - now


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Injector run: prove if emittance can be preserved at high energy

Linac run: Not all hardware have been installed/existed

Beam commissioning in parallel to hardware/software commissioning

Early commissioning to identify

⇒ building blocks for controls required for operation

⇒ additional hardware/electronics/diagnostics/controls

⇒ hardware problems

⇒ reliability and stability

Several stages for commissioning:

1. Test of general functionality of component or subsystem

2. Stability and reproducibility of operation

3. High precision measurement and consistent checks with simulations


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• Upgrade of injector II

• Booster with 4 SC cavities + 4 to further accelerate

• 3rd harmonic cavity to straighten the longitudinal phase space

• Laser with longitudinal flat-hat profile

• Commissioning up to ACC2

RF gun

4 MeV 150 MeV

bunch compressor

ACC1 (M2*)

ACC2(M1*) ACC3(M3*)

Laser

3rd

harmonic cavity diagnostic section

beam dump

12 MV/m 20 MV/m

§ 3rd harmonic cavity not yet installed

§ Laser with longitudinal Gaussian profile

§ Commissioning up to ACC2

§ operated all 8 cavities at 12 MV/m -> 100 MeV

Final stage: During spring 2004:


� ��• RF Gun:

21-Feb-2004 start RF conditioningMarch 04 5 Hz, 900 s, 3 MW

10 Hz, 450 s, 3 MWfirst beam in gun section

April 04 measurements of gun performance» Quantum efficiency of photo cathode» Transmission and beam size» Phase measurements» Energy, energy spread» Dark current

• Injector:April 04 start injector commissioning

» High gradient test of cavity» Emittance measurements» HOM for beam based alignment» CSR measurements

07-Jun-2004 end commissioning


� �� • Full transmission through the narrow dipole

chamber only for solenoid current above 280 A

• Focus on last screen before ACC1 (I = 295 A)

• Bucking off, 1 nC, 3 mm diam. laser, 40 dg phase

• Data don’ t fit well at focus:probably a optical resolution problem

• Significant steering required280 A


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charge (nC)

1 deg

Several scan in a row:

Reproducibility of RF gun phase adjustment:

Acceptance versusRF phase &Solenoid current

When special cuts are applied

Sole

noid

cur

rent

[A

]Gun phase [deg]


��• momentum measurements in dispersion section after RF gun• reflected power is corrected for• p versus Pfwd: data fit well with the simulation;

p versus phase: agreement less good


" �� • measurement in March 2004 (10 Hz, 400 s, 3.2 MW): max. 230 A

and in June 2004 (5 Hz, 100 s, 3.2 MW): max. 160 A

• No critical dark current levels observed

• But 100-200 A already contribute to beamlineactivation

main solenoid current (A)

dark

cur

rent

(uA

)

dark

cur

rent

(uA

)

2nd FCW

ork

poin

ts

1st and 2nd faraday cup, Pfor=3.2MWDark current entrance of ACC1 (2nd FC)


# ��• electro-polished cavity installed at #5 in ACC1• cavity is equipped with Piezo-tuner• cavity RF test predict G = 36 MV/m (RF power measurements)• RF calibration confirmed with energy meas. of beam in BC2⇒ Successful installation of

high gradient cavity in acc. module.

Cavities limits ACC1:C1 (Z54) 18 MV/m C2 (Z51) 16 MV/m Lower limit for ACC1 C3 (D42) 20 MV/m C4 (D37) 27 MV/m power limited C5 (AC72) 36 MV/m no FE C6 (C47) 23 MV/mC7 (Z53) 20 MV/m large FE large

Lorentz forces C8 (AC69) 18 MV/m large FE


$��% ��& ��'��%OTRWS

OTRWS

OTRWS

OTRWSQF QF QFQD QD QD

0.95 m 1.9 m0.46 m 0.49 m

Matching quadrupole = 45°

Camera

3 Lenses

3 Filters

Mirror

OTR station (Frascati)• Four monitor method using OTR monitorsor wire scanners– During commissioning only the OTR monitors in operation

• Beam size measured at four screens in a FODO lattice of six quadrupoles (fixed quad current)

• Emittance and Twiss parameterscalculated from the measured beam sizes and beam size errors using chi-square fitting (90% of beam image)

• Gun parametersas optimized at PITZ (except solenoid)

• Measurements with by-passed bunch compressor

E=100MeV


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4DBC2 6DBC2

10DBC28DBC2

Beam images from 4 OTR screens: phase advance of 45°, 1 nC, magnification =1


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• Normalized emittance in vertical direction < 2.0 umhor izontal direction < 2.5 um

• Large scattering in measurement results for x

• Systematic studies for horizontal orbit versus emittance still open.

• Emittance growth may caused by – Laser mirror – Kicks in ACC1– Alignment problems GUN/ACC1

• Nevertheless, a very promising though still preliminary result

• Study of systematic in beam size determination and measurement errors not completed yet


# ( ) *� ��• The signal of a dipole mode in a cavity can be used to

determine the beam position• Due to different polarization x and y can be measured • Handle to investigate misalignment gun/module

example for vertical steering and dipole mode response in C1


$��!��• Energy spread measured from horizontal beam profile in the dispersivesection of the bunch compressor (OTR screen) • Residual energy spread estimated from the rising edge about 30 keV (rms), tail of about 200 keV• Energy stable within 0.12 % measurements with single bunches on-crest acceleration (LLRF FB on but low gain)

If slow drift is removed ~ 0.12%

Cal = 24 keV/pixelE0 =100 MeV

Energy (a.u.)

Inte

nsity

(a.

u.)

Energy spread


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~ 15 m transfer lineZ-cutQuartzwindow


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Input polarizer

Beam splitter

Roof mirror

Inputbeam

Parabolic mirror

Detectors removed, types used DTGS, Pyro, Golay

Martin-Puplett Far Infrared Inter ferometer :


First autocorrelation taken:

Spectra for different compression phase:

Expected Maximum ofcompression

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10 bunches, 1 nC, Gun = -40 degred, green: DTGS detectors in TOSYLAB blue: Sum of both DTGS black: Pyro P1-65 (100 MOhm) at 10DBC2

Compression monitor: coherent power ~ 1/σz

⇒ ideal suited to measure relative bunch lengths

Max. compression

On-crestCTR(CDR)

Two maxima for CSR observed!

��% ��%

Acceleration phase ACC1 [deg]

Det

ecte

d si

gnal

s [V

]


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• Commissioning of linac:August dark current measurements C6@ACC5September restart of operation gun

PS commissioned up to exit BC2beam operation ACC1 with 4*12.5 +4*18.5 MV/mBPM commissioning and calibration in BC2coarse cavity phasing of ACC2&ACC3

October transmission through BC3transmission up to collimator sectioncavity phasing of ACC2&ACC3cavity phasing of ACC4&ACC5all PS for magnets in bypass available

November transmission to dump through bypass


��'�,• after coarse phasing of ACC2&ACC3 (21-Oct-2004):

Good transmission with BC3 on/off


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• Alarms: HV type of beam losses• Not yet connected to linac interlock• Very useful for steering and beam adjustments• Dark current fire BLM interlock (attenuation)

beam

Only gun d.c.

ACC1 + gun d.c.


��!• after commissioning of by-pass dipoles: ~ 25% transmission• few days later ~ 75% transmission• empirical optics …


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• aperture problem in gun section (dipole chamber) ⇒ limits regime for beam operation

• missing BPM in gun dump line⇒ no control of energy stability in macro pulse

• misalignment in gun area⇒ dark current collimator cannot be used

• BPMs in BC2 & BC3 does not work⇒ no online control on energy after ACC1 and ACC2&3

• only about 360 MV energy at BC3 (400MeV design/required?)⇒ higher space charge effects

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Holger Schlarb DESY 22607 Hamburg · 09.11.2004 Holger Schlarb, DESY 8 " ˙ • measurement in...

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