results from the 's1-global' cryomodule tests at kek (8-cav. and drfs operation)

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Results from the 'S1-Global' cryomodule tests at KEK

(8-cav. and DRFS operation)

Shin MICHIZONO (KEK)

LOLB-2 (June, 2011)

OutlineI. 8-cavity installation (S1 global) Total eight cavities are installed. Rather short time operation (for total 3 months, Mon. to Fri. from 1PM to 7PM.) No beam operation With circulators at individual input couplerDynamic detuning control with piezo Vector sum operation Quench analysisII. DRFS operation (aiming for ilc) One klystron drives two cavities. Total 2 klystrons are used. No beam operation Without circulators Dynamic detuning control with piezo Slow detuning control with piezoIII. Future plan

Related topics-Performance-Diagnostics-Piezo control(8cav. &DRFS)-Quench phenomena (8cav. &DRFS)-Rf overhead (8 cav. &DRFS)- Circulator-less (DRFS)

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S1 Global LLRF for 8 cav. operation All the cavities are driven by 5 MW klystron.

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Digital LLRF system using an FPGA board on cPCI. 10 16bit-ADCs are installed.

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loaded-Q interlock Calculate the loaded Q from the decay of the rf signal The interlock works well and contributes to the lower heat load to the cryogenics.

RF off

RF offDoneLOLB-2 (June, 2011)

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Real time detuning monitor

The real time detuning monitor is quite helpful to adjust the Piezo tuners.

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detuned

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Stabilities at 26 MV/m operation

0.0067%rms （ in amplitude),16.5mdeg.rms(in phase) @690 ～ 1590us

By T. Matsumoto

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RF stabilities during 2H operation

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Vector sum amplitude and phase are kept constant during 2H operation.

Gradient

Amplitude stability

Phase stability

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Dynamic detuning compensation with piezo

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Piezo works well to compensate the dynamic detuning

Detuning change during 2H operation

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DESY: 33Hz, FNAL:12~38Hz, KEK: 5~10Hz

quench

Rather stiff at A-1~4. (~1/4 compared with C-1~4)

FNALDESY

KEK KEK KEK KEK

Ql change during operation

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Ql changes are also observed at KEK. This is still open question. (difficult to explain by only coupler lod)

FNALDESY

KEK KEK KEK KEK

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Cavity equation

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The cavity should satisfy the differential equation. In addition directivity (~20dB) of rf monitor-coupler should be concerned. -> The directivity can be corrected using this formula.

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Vሶ=−൬ω12− j∆ω൰V+2ω12Vfor Vcavሶ − j∆ωVcav =ω1/2Vdif Vdif = Vfor −Vref Vcavሶ − j∆ωVcav =ω1/2Vdif VcavRሶ ＋∆ωVcavI =ω1/2VdifR VcavIሶ −∆ωVcavR =ω1/2VdifI ω12 =

12 ddta�Va�2Vfor2 −Vref2

𝐐𝐥=𝛚𝟎൫𝐕𝐟𝐨𝐫𝟐 −𝐕𝐫𝐞𝐟𝟐 ൯𝐝𝐝𝐭a�𝐕a�𝟐

Quench phenomena

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Loaded Qs are calculated from cavity differential equation. Only the end of rf pulse shows the quench.

Rather stiff at A-1~4. (~1/4 compared with C-1~4)

Quench phenomena (2)

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Detuning change at C-4 affects the VS leading to C-1 Quench

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Schematic of the DRFS at S1-global

DRFS #1

DRFS #2

MA modulator

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DRFS klystron and WG system with module

Feb.8 :

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DRFS klystron and WG system

Feb.8 :

Phase shifter

Phase shifter

Some photos

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DRFS #1

DRFS #2

Modulator on the ground

LOLB-2 (June, 2011)

Some photos (2)

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DRFS #1

Phase shifter

MA modulator

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HLRF and LLRF

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Magic-T and WG system LLRF rack is located just downstream of cryomodule-> radiation dose will be measured.

S1 Global 3rd stage (DRFS) （ 1 ） Digital system is located in the tunnel Fast interlock (and Arc detectors, VSWR meter) are located on the ground. cPCIs are used for the monitor and also they are the backup digital system.

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Field regulation with uTCA

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cERL like uTCA FPGA system was installed. An FPGA board have 4 16-bit ADCs and 4 16-bit DACs. Two cavity-pickups, klystron output, reflection are observed. The system was located in the tunnel.

RF distribution at DRFS

One klystron drives two cavities. Circulator-less system.Same (amplitude and phase) reflection signals go to the dummy load.(blue line) Un-balanced reflection signals move to the klystron. (red line) -> careful operation is required to protect the klystron.

Phase-shifters are introduced to evaluate the system. (not to be used at ilc-DRFS)

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Circulator-less system Elimination of circulators are proposed at DRFS. The study to eliminate the circulators were partly carried out at STF-1. However, there was a big circulator between cavities and a klystron. This is the first time to eliminate all the circulators.

Cavity input

Normalized by klystron output

Cavity input exists even after RF off

With circulators Without circulators

| Vf |

| Vf |

Vf a

mpl

itude

rat

io (

%)

Vf a

mpl

itude

rat

io (

%)

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Results at STF-1

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Cavity equation

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The cavity should satisfy the differential equation. In addition directivity (~20dB) of rf monitor-coupler should be concerned. -> The directivity can be corrected using this formula.

LOLB-2 (June, 2011)

Vሶ=−൬ω12− j∆ω൰V+2ω12Vfor Vcavሶ − j∆ωVcav =ω1/2Vdif Vdif = Vfor −Vref Vcavሶ − j∆ωVcav =ω1/2Vdif VcavRሶ ＋∆ωVcavI =ω1/2VdifR VcavIሶ −∆ωVcavR =ω1/2VdifI ω12 =

12 ddta�Va�2Vfor2 −Vref2

𝐐𝐥=𝛚𝟎൫𝐕𝐟𝐨𝐫𝟐 −𝐕𝐫𝐞𝐟𝟐 ൯𝐝𝐝𝐭a�𝐕a�𝟐

Diagnostics (Ql evaluation)

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The simple Ql estimation from decay curve does not work when the rf input exist after rf switched off. The calculated Ql values agree well between filling and decay. Although simple Ql calculation is useful for interlock, this is not sufficient for diagnostics.

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Ql at filling

Cav1

Cav2

Ql at decay

Ql from decay

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Typical operation of VS control

Under the low reflection condition, VSWR is ~1.1.

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Pf

Pb to kly.

Detuning and Ql under typical operation

Loaded Qs calculated simple time decay are not correct.

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Cav. C-1

Cav. C-2

Red:Ql by decay

Blue: Ql by cavity eq.

Un-matched operation with VS control(different detuning)

Reflection to the klystron is ~25kW (max VSWR=3) Vector sum is still regulated. (0.04%rms, 0.06deg.rms)

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Pf

Pb to kly.

f1>f2

Un-matched operation (detuning and Ql)

Although Qls by decay show low-value, Qls based on cavity equation show reasonable values.

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Cav. C-1

Cav. C-2

Red:Ql by decay

Blue: Ql by cavity eq.

Un-matched operation with VS control(different waveguide-length)

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Reflection to the klystron is ~20kW (max VSWR=2.8) Vector sum is still regulated. (0.015%rms,0.07deg.rms)

Pf

Pb to kly.f1~f2

Un-matched operation (detuning and Ql)

Ql by decay: ~4e6 Ql by cavity equation: ~2.5e6 43

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Cav. C-1

Cav. C-2

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Adaptive detuning correction via EPICS

DC piezo bias is controlled every ~2 min. for detuning correction. The detuning after filling were kept constant

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1

1.2

1.4

1.6

1.8

2

2.2

2.4

2.6

0 50 100 150 200 250

Piez

o co

ntro

l offs

et [V

]

time [min.]

detune control

control off

Even these simple (and slow) detuning correction looks promising to compensate the long-time detuning fluctuation (microphonics).

Piezo output to change from 0Hz to -50Hz

Detuning correction

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RF waveform and detuning

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RF overhead @flat-top

4%

Minimum 3% rf overhead is necessary.

If we allow 50Hz detuning, 7% overhead is required .

10% overhead necessary.

11%

Average power

Variation inside pulse

Long term stability (microphonics)

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A-2

A-3

No piezo controlNo piezo control

Microphonics are about 3~5Hz rms. Since KEK cavities are stiff enough, the effect of adaptive piezo control is not clear.

Adaptive control

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Future plan at STF Quantum beam project: with beam from Jan.2012. STF-2 project: with beam from April 2013.

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Future planQuantum beam STF Phase2

Pulse length 1ms 0.9ms

Repetition rate 5Hz 5Hz

Bunch Spacing 6.15ns (162.5MHz) 369.27ns (2.708MHz)

Number of bunch/pulse 162500 2437

Bunch charge 62pC 3.2nC

Total charge /pulse 10,000nC 7,798nC

Beam current 10mA 8.7mA

Bunch length 12ps(Laser, FWHM) 10ps(Laser, FWHM)

Max. beam energy 40MeV 21.5MeV

Beam power 2.0kW (40MeV beam) 0.8kW (21.5MeV beam)

• RF gun cavity and input coupler were fabricated by FNAL. (DESY-FNAL-KEK collaboration)

• FNAL delivered gun cavity and input coupler in November 2009.

• RF process up to 1.7MW in 2010.

• More high power process (3.5MW) and beam extraction in 2011.

DESY-FNAL design RF gun,FNAL fabrication.

input coupler

Photocathode insertion

Photocathode RF gun for beam supply to Cryomodules

Photocathode RF-gun in STF

gun cavity

cavity

photocathode chamber

input coupler

Solenoid magnet

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Two 9-cell cavities ： 15.2MV/m operation

Capture Module

Cavities: MHI-012, MHI-013

Similar Structure to ILC Cryomodule, except the length

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Thank you for your attention

results from the 's1-global' cryomodule tests at kek (8-cav. and drfs operation)

Documents

beam operation

h operation

short time operation

piezo slow detuning

real time detuning monitor

drfs circulator

s1global cryomodule

piezo tuners