XFEL SRF Accelerating Module Prototypes Tests at DESY Fermilab Seminar, July 21st 2011. Denis Kostin, MHF-SL, DESY

XFEL SRF Accelerating Module Prototypes Tests at DESY

Fermilab Seminar, July 21st 2011.

Denis Kostin, MHF-SL, DESY.


2

Denis Kostin, MHF-SL, DESY. Fermilab Seminar, July 21st, 2011

Abstract

The Cryo Module Test Bench (CMTB) at DESY is used since several years for the SRF module tests. Three XFEL prototypes modules, PXFEL1,2,3, were tested using this facility. Summary of the last SRF modules testing activities is presented. Module test infrastructure is described in detail, new XFEL testing facility, AMTF, progress and plans are discussed. Module and cavities performance data for the XFEL prototype modules are presented.


3


Overview

Module Test Stand CMTB

Module Test Procedure

Module Test Data

XFEL Prototypes Tests

AMTF overview

Summary


4


Cryo Module Test Bench


5


70K shield

Cavity type TESLANumber of cavities 8Cavity length 1.038 mOperating frequency 1.3 GHzR/Q 1036 ΩAccelerating Gradient 20..35 MV/mQuality factor 1010

Qext (input coupler) 3×106

Operating temperature 2 K

LHe cooling 2K / 31mbarHERA cryoplant is used

12m

4K shield

input coupler

2 phase LHe pipe

He gas return pipe

Module / Cryogenics


6


SRF module

10 MW klystron (MBK)

WG switchcirculator

modulator

coupler 1 coupler 8

CMTB RF System


7


CMTB LLRF Systemdata acquisition

data acquisition


8


Two gamma detectors are placed near the beam line on both ends of the module (by the end-caps).

Gamma detector "GUN"Gamma detector "DUMP"

module

Module Gamma Radiation Measurement


9


Module

Coupler

Common pumping line

Ion Getter PumpTi Sublimation Pump

Beam line

TSP/IGP connected in parallel and IGP used as a vacuum gauge.

Module Vacuum System


10


Module / Input RF Coupler

warm part

waveguide part

RF power coupler

cold 70K window

cold partwarm 300K window

cavity

cavity


11


3 times e- (charged particles)

light in coupler vacuum

light in wave guide (air side)

temperature cold ceramic

temperature warm ceramic

vacuum coupler

vacuum cavity

bias voltage

cryogenic OK

low level R

F gate on klystron

all thresholds are hardware set

Coupler Technical Interlock


12


RF Conditioning Data / Controls

A.Goessel, DESY.


13


1. RF Cables Calibration. TDR cables check Dir.Couplers / Circulators: get calibration data. Calibrate RF power measurement cables with attenuators

at 1.3 GHz ( P for/ref att. 93 dB, P trans/HOM 40 dB ) Calibrate RF power measurement cables with attenuators

at 1…4 GHz ( optional ) Make RF calibration summary table

2. Technical Interlock / Sensors. Check the sensors (e-, Light, Spark, Temp.) Set the hardware interlock thresholds Check the interlock

3. RF source / Waveguides / LLRF. Klystron / LLRF check on the load WGs visual check System check / RF leak check at low power (1 kW pro coupler)

4. Warm Input RF Couplers Conditioning ( all / 1234 + 5678 ). Run the standard conditioning program:

20, 50, 100, 200, 400 s pulse lengths up to 1MW (min. 700kW), 800, 1300 s pulse lengths up to 600 kW, 2 Hz rep.rate. (If the klystron gives not enough of RF power divide the system into the successive tests in such a way that each coupler will be conditioned up to 1MW.)

Module Test Procedure (1)


14


5. Cooldown to 2K. Run coupler conditioning (RF power sweep) during the

cooldown from 300K to 200K. 6. Cavities Spectra measurements.

Measure the fundamental mode spectra Measure the cavities HOMs spectra and Qload Calibrate the cold RF cables at 2K

7. Cavities Tuners Test. Test the cavities step-motor frequency tuners Tune the cavities to the 1.3GHz using the Network Analyzer

8. Couplers Qload measurement. Measure the Qload vs antennae positions,

check Qload.MIN and Qload.MAX using the Network Analyzer Set Qload = 3106 for each coupler

9. Cavities On Resonance. Cavities fine-tuning to the 1.3GHz using LLRF system Qload, Kt calibration ( Eacc=kt(Ptrans)

1/2 )



15


10. Cold Input RF Couplers and Cavities Conditioning. Short RF pulse test at 2K on resonance (100 .. 500 s pulse lengths up to 700kW),

coupler / cavity conditioning (HPP). 11. Module Performance Measurement.

Module Eacc.MAX measurement at 2 Hz rep.rate with 500 + 100 s flat-top pulse. Module accelerating gradient measurement at 10 Hz rep.rate

with cryo losses (Qo) and radiation measurements (500 + 800 s flat-top pulse). Gamma Radiation / Dark Current measurements. WG power redistribution possibilities check in case of

too different cavities limits (Eacc.MAX > 5 MV/m) 12. Single Cavities Measurements.

Detune all cavities except the one under test Flat-top pulse measurements at 10 Hz rep.rate

with cryo losses (Qo) and radiation measurements Investigate the cavities limits at 10 Hz rep.rate

13. Cryo system performance test. Static Cryogenic Losses measurement, temperature measurements. Stretch-wire monitor module geometry deviations measurements. Cool-down cycles.



16


Module Test Data

coupler RF power conditioning8 couplers

coupler sensors data history 8 couplers

kt (cavity probe calibration) 8 cavities

Qload (at 1.3 GHz) 8 cavities

Qext_probe, Qext_HOM1/2 (at 1.3 GHz) 8 cavities

frequency / spectra 8 cavities

Eacc.X.start (single) 8 cavities

Eacc.max (single, no Qo) 8 cavities

X-rays (Eacc.max) 8 cavities

Qo(Eacc) module

X-rays(Eacc)module

cavity conditioning data 8 cavities

HOM couplers Qext(Freq_HOM) 8 cavities

coupler / cavity vacuum pressure e- probes signal (voltage) light (PM) signal (voltage) – not for the

XFEL / AMTF spark detector (diode) signal (voltage) cold ceramics temperature (PT1000) T70K

warm ceramics temperature (IR/PT1000) T300K

coupler sensors data RF power / cavity gradient gamma radiation (X-rays) LHe level / pressure


17


Cryosystem/Cooldown Test

0 50 100 150 200 250 3001297.5

1298.0

1298.5

1299.0

1299.5

1300.0

m

ode

freq

uenc

y [M

Hz]

temperature [K]

C1 C2 C3 C4 C5 C6 C7 C8

PXFEL3 / CMTB

Cavity -mode resonance frequency vs LHe temperature

temperature measurement: temperature sensors (cavities/couplers + cryogenics) data are stored.

multiple cooldown / warm-up test.

cavity resonance frequency measurement during the cooldown.

cryogenic losses measurement based on temperature and LHe flow data: 2K, 4K and 70K static (infrastructure) and dynamic (RF power) losses.

stretch-wire based module dimensional changes measurements.


18


mVPk

eL

PQQ

R

E

transt

Qtf

cavity

forloadsh

ACCload

fill

,

14 0

evaluated error margins for accelerating gradients in this test are about 10..16%.

RF Power Calibration

Rsh/Q=1030, Lcavity=1.035m, Qload=3106, f0=1.3GHz, Pfor5kW,tfill=1300s (for calibration, 500s for flat-top)

raterept

PP

PQR

LEQ

pulse

cryoloss

loss

acc

.

;2

0

HOMtransext

ext

accext

PPP

PQR

LEQ

,

;2

flat-top RF power pulse

Cavities gradients for the 1.3 ms rectangular pulse

RF Calibration / Cavity Test


19


-2 0 2 4 6 8 10 12 14 16 18 20 22 24

106

107

module6 / MTS. Couplers Qload

1 2 3 4 5 6 7 8

Qlo

ad

distance out [mm]

1 2 3 4 5 6 7 8105

106

107

PXFEL2 cavities input coupler Qload

range

Qlo

ad

1 2 3 4 5 6 7 818

19

20

21

tuni

ng r

ange

[m

m]

Input RF Couplers coupling tuning range measured at CMTB

operating value Qload=3106

RF Couplers Qload Tests


20


HOM Spectra measurements

1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5103

104

105

106TM110 TM011Q

load

f [GHz]

TE111 The intense electron bunches excite eigenmodes of higher frequency in the resonator which must be damped to avoid multibunch instabilities and beam breakup. Modes having high Rsh are more dangerous:


21


RF Couplers Conditioning History/Data (1)

Light IL events

20 s pulses 50,100,200,400,800 s pulses

Light IL events


22


RF Couplers Conditioning History/Data (2)1300 s pulses

TSP fired

Light IL events

TSP saturated

cryo

wor

ks

cryo

wor

ksRF power sweep at 1300 s pulse

coup

ler 1

,2,6

,8 a

ctivi

ty


23


RF Couplers Conditioning Time

M6-1

256

M6-3

478

M7-1

256

M7-3

478

M5-3

478

M5-1

256 M8 M3**

PXFE

L1

PXFE

L2

PXFE

L3

PXFE

L2_1

0102030405060708090

100110120130140150

not f

inis

hed

C1,

C3

war

m p

art l

ight

TS

P s

atur

ated

module

CMTB

cou

pler

s te

st:

RF

pow

er r

ise

time

[hr] pulse length:

1300s 800 s 400 s 200 s 100 s 50 s 20 s

PMAX=700kW

IGP vacuum pressure IL limit set to 10-6 mbar

TS

P s

atur

ated

C1

war

m p

art l

ight co

uple

r w

arm

par

ts p

robl

ems


24


XFEL Prototypes Tests

Module Tests on CMTB at DESY

Module Date comment

PXFEL1 Jun.2009 first test

PXFEL2 Oct.2009 first test

PXFEL3Aug.2010 first test

Feb.2011 after disassembly: single cavities tests

PXFEL2_1 Mar.2011 after reassembly at CEA Saclay


25


1 - AC129 2 - AC123 3 - AC125 4 - Z143 5 - Z103 6 - Z93 7 - Z100 8 - AC1130

5

10

15

20

25

30

35

40

FLASH 30MV/m XFEL goal

13.07.2009

EA

CC [

MV

/m]

cavity

Cavity tests: Vertical ( CW ) Horizontal (10Hz) CMTB M8 (10Hz) CMTB (10Hz)

very

long

CW

cond

ition

ing

Cavities gradient limits

1 - AC129 2 - AC123 3 - AC125 4 - Z143 5 - Z103 6 - Z93 7 - Z100 8 - AC1130

5

10

15

20

25

30

35

40

Cavities Field Emission

13.07.2009

EA

CC [

MV

/m]

Module PXFEL1 MTS: FE start

X > 10-2 mGy/min

max.gradient

cavity

1 - AC129 2 - AC123 3 - AC125 4 - Z143 5 - Z103 6 - Z93 7 - Z100 8 - AC11310-5

10-4

10-3

10-2

10-1

H

M

MM

V

V

V

cavity 8 tested in horizontal cryostat before module assembly (H)

cavities 1..4 tested in vertical cryostat before module assembly (V)

13.07.2009

Xra

ys [

mG

y/m

in]

X-raysmax

:

V/H/M test MTS.Gun MTS.Dump

single cavities radiation at Eacc.max

cavity

cavities 5,6,7 were in the module 8 at the same positions (M)

V

Module Test Results: PXFEL1 Data (1)

measured (CMTB) XFEL specification

RF power, kW 120 230 200

4K losses, W 0.1 0.26 0.5

70K losses, W 2.5 3.75 6.0

static cryo-losses:


26


10 15 20 25 300

2

4

6

8

dyn

am

ic (

RF

) lo

sse

s P

cryo

[W]

<Eacc

> [MV/m]

10 Hz

10 15 20 25 30109

1010

Q0

<Eacc

> [MV/m]

10 15 20 25 3010-5

10-4

10-3

10-2

10-110 Hz

X-r

ays

[mG

y/m

in]

<Eacc

> [MV/m]

XGun

XDump

Flat-top pulse 500+800μs operation at 10 Hz

Module Test Results: PXFEL1 Data (2)

dynamic cryo-losses

gamma radiation

Q0(Eacc)


27


Module Test Results: PXFEL2_1, PXFEL3 Data (1)

1-Z141 2-AC150 3-Z133 4-Z139 5-AC122 6-AC121 7-AC128 8-AC11505

101520253035 MP

MP

XFEL goal

PXFEL2_1Cavities gradient limits

12.05.2011

EA

CC [M

V/m

]

cavity

Cavity tests: Vertical ( CW )

Module Test Stand: PXFEL2 (10Hz) PXFEL2_1 (10Hz)

MP

1 - Z135 2 - AC124 3 - Z88 4 - Z134 5 - Z101 6 - AC127 7 - Z140 8 - Z9705

101520253035

PXFEL3Cavities gradient limits

HH

XFEL goal

25.02.2011

EA

CC [M

V/m

]

cavity

Cavity tests: Vertical ( CW ) CMTB (10Hz) Vert./Hor.(10Hz)

MP

FE

FE

several cavities suffered from degradation after the string assembly


28



1-Z141 2-AC150 3-Z133 4-Z139 5-AC122 6-AC121 7-AC128 8-AC11510-5

10-4

10-3

10-2

10-1

100

PXFEL2_1

12.05.2011

Xra

ys [m

Gy/

min

]

PXFEL2 Gun PXFEL2 Dump PXFEL2_1 Gun PXFEL2_1 Dump


cavity

1-Z141 2-AC150 3-Z133 4-Z139 5-AC122 6-AC121 7-AC128 8-AC1150

5

10

15

20

25

30

35

Cavities Field Emission12.05.2011

PXFEL2_1

EA

CC [M

V/m

]

FE start: PXFEL2 PXFEL2_1

X > 10 -2 mGy/min: PXFEL2 PXFEL2_1

cavity 1-Z135 2-AC124 3-Z88 4-Z134 5-Z101 6-AC127 7-Z140 8-Z970

5

10

15

20

25

30

35Cavities Field Emission

13.09.2010

EA

CC [M

V/m

]

FE start

X > 10-2 mGy/min max.gradient

cavity

PXFEL3

1-Z135 2-AC124 3-Z88 4-Z134 5-Z101 6-AC127 7-Z140 8-Z9710-5

10-4

10-3

10-2

10-1


H

H

25.02.2011

Xra

ys [m

Gy/

min

]

X-raysmax

:

Vert. test MTS.Gun MTS.Dump V/H test

cavity

PXFEL3


29



14 16 18 20 22 24 26 28 30 320123456789

PXFEL2_1

cav.

7 de

tune

d

cav.

6 de

tune

d

cav.

1 de

tune

d

cav.

3 de

tune

d

dyna

mic

(R

F)

loss

es P

cryo

[W

]

<Eacc

> [MV/m]

10 Hz

14 16 18 20 22 24 26 28 30 32109

1010

cav.

7 de

tune

d

cav.

6 de

tune

d

cav.

1 de

tune

d

Q0

<Eacc

> [MV/m]

cav.

3 de

tune

d

14 15 16 17 18 19 20 21 22 23 24 250

1

2

3

4PXFEL3

cav.

3,6,

7 de

tune

d

cav.3,6 detuned

dyna

mic

(R

F)

loss

es P

cryo

[W

]

<Eacc

> [MV/m]

10 Hz

14 15 16 17 18 19 20 21 22 23 24 25109

1010

cav.

3,6,

7 de

tune

d

Q0

<Eacc

> [MV/m]

cav.

3,6

detu

ned

14 15 16 17 18 19 20 21 22 23 24 2510-6

10-5

10-4

10-3

10-2

10-1

cav.

3,6,

7 de

tune

d

cav.3,6 detuned

X-r

ays

[mG

y/m

in]

<Eacc

> [MV/m]

XGun

XDump

14 16 18 20 22 24 26 28 30 3210-5

10-4

10-3

10-2

10-1

100

cav.

7 de

tune

d

cav.

6 de

tune

d

cav.1 detuned

cav.

3 de

tune

d

X-r

ays

[mG

y/m

in]

<Eacc

> [MV/m]

XGun

XDump


30



0 5 10 15 20108

109

1010

C3 Z88 C6 AC127

Q0

Eacc

[MV/m]

PXFEL3

0 5 10 15 2010-5

10-4

10-3

10-2

C3 Z88 C6 AC127X

-ray

s [m

Gy/

min

]

Eacc

[MV/m]

PXFEL3 degraded cavities horizontal cryostat test after the string disassembly

low field emission,very high cryo-losses up to 20W before breakdown


31



20 21 22 23 24 25 26 27 28 29 30 3110-6

10-5

10-4

10-3

10-2

10-1

Gam

ma

Rad

iatio

n [m

Gy/

min

]

EACC

[MV/m]

module gun module dump vertical

1.Z135

20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 3510-6

10-5

10-4

10-3

10-2

10-1

Gam

ma

Rad

iatio

n [m

Gy/

min

]

EACC

[MV/m]


2.AC124

no gamma radiation in vertical test

15 16 17 18 1910-5

10-4

10-3

10-2

Gam

ma

Rad

iatio

n [m

Gy/

min

]

EACC

[MV/m]

module gun module dump horizontal

3.Z88

23 24 25 26 27 2810-5

10-4

10-3

10-2

Gam

ma

Rad

iatio

n [m

Gy/

min

]

EACC

[MV/m]


5.Z101

22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

10-5

10-4

10-3

10-2

10-1

Gam

ma

Rad

iatio

n [m

Gy/

min

]

EACC

[MV/m]


4.Z134

12 13 14 15 16 17 18 19 2010-5

10-4

10-3

10-2

10-1

Gam

ma

Rad

iatio

n [m

Gy/

min

]

EACC

[MV/m]

horizontal vertical

6.AC127

no radiation measured in module

21 22 23 2410-6

10-5

10-4

10-3

Gam

ma

Rad

iatio

n [m

Gy/

min

]

EACC

[MV/m]


7.Z140

15 16 17 18 19 20 21 22 23 24 25 26 2710-6

10-5

10-4

10-3

10-2

10-1

Gam

ma

Rad

iatio

n [m

Gy/

min

]

EACC

[MV/m]


8.Z97

PXFEL3 cavities gamma radiation measurements in module and after the string disassembly

Test stands infrastructure radiation damping up to 103


32



HOM coupler multipactor effect in XFEL prototype modules at 1 .. 2 MV/m cavity gradient value

RF pulseamplitude change

cavity detuning effect

PXFEL3.C2.HOM1

gap

PXFEL3.C2.HOM1

PXFEL2_1.C2.HOM2

anomalous HOM coupler signal peak


33



PXFEL2_1 cavities string was not reassembled, but vented from dump-side (quadrupole and cavity 8). PXFEL3 cavities were tested after the disassembly at DESY.

PXFEL2_1 Cavity 1 did show strong multipacting at 19..21 MV/m with high FE (up to 3 mGy/min) and BD, it was successfully conditioned, this was the case also with module PXFEL2. Cavity 4 had MP at 20..21 MV/m as well. Cavity 3 is limited at 16.2 MV/m, without field emission (FE), like in PXFEL2. Cavity 5 went to 37.5 MV/m an was RF power limited. Cavities 7 and 8 showed strong FE increase (mostly at cavity 7), it was partially conditioned during the test. Accelerating gradient limits are close to PXFEL2 ones, no degradation.

Module PXFEL3 suffered from two cavities degradation: cavity 3 is limited at 18.5 MV/m with very low FE, cavity 6 is limited at 19.2 MV/m – no FE measured. Cavities 3 and 6 show high dynamic cryo-losses just before the quench. Cavity 1 did show multipacting at 22.5 MV/m, it was successfully conditioned. Cavities 4 and 8 have high FE, starting from 15 MV/m. Stable operation was possible with average gradient of 17.5 MV/m with low gamma radiation (10-3 mGy/min). Cavities retested after the module disassembly showed the same gradient limits. Both cavities 3 (Z88) and 6 (AC127) did have high cryo-losses (up to 20 W) in horizontal test just before BD, cavity 6 showed FE (initially high and partially conditioned).

Both tested modules suffered from some cavities degradation, but the degraded cavities behavior is different. Cavity degradation phenomena is under investigation.

HOM coupler multipacting effect at 1..2 MV/m cavity gradient was detected in XFEL prototype modules cavities.


34


AMTF overview

2 cavity test stands (x4), 3 module test stands (5 MW klystron)


35


Summary

High and low power RF tests, as well as cryogenic tests are conducted on the accelerating SRF modules and cavities/couplers using the Cryo Module Test Bench (CMTB) at DESY. 10 SRF modules (including one 3.9 GHz module) tested until now at CMTB. XFEL Accelerating Module Test Facility (AMTF) is under construction.

SRF module test procedure was developed together with test data structure. Module test data is stored for each test and used for the performance analysis. New AMTF facility test data structure will be based upon CMTB and TTF data structure with implementation of module centered data clusters (not only cavity and couplers).

First three XFEL prototype modules PXFEL1,2,3 were tested at module test stand CMTB at DESY. Coupler and cavity conditioning procedure was done with PXFEL modules.

In PXFEL1 cavities gradients from 27 to 36 MV/m are reached, module operation with average gradient of 30 MV/m using tailored RF power distribution is possible. PXFEL1 is used in FLASH (ACC7). PXFEL2 (PXFEL2_1) and PXFEL3 modules suffered from some cavities degradation.

Documents

XFEL SRF Accelerating Module Prototypes Tests at DESY Fermilab Seminar, July 21st 2011. Denis Kostin, MHF-SL, DESY