Download Horizontal Test Cryostat HNOSS

Test stand and SRF cavity test plan
at the FREIA Laboratory
Han Li
On behalf of FREIA team
FREIA Laboratory, Uppsala University
13th of June 2017
What and Whom?
Facility for Research Instrumentation and Accelerator Development
State-of-the-art Equipment
cryogenics
- liquid helium
- liquid nitrogen
control room
- equipment controls
- data acquisition
Competent and motivated staff
collaboration with physics (IFA),
engineering (Teknikum), TSL
and Ångström workshop
Funded by
KAWS,
Government,
Uppsala Univ.
Han Li 13th June 2017
vertical cryostat
RF power sources
3 bunkers
with test stands
horizontal cryostat
2
Responsibility for ESS Accelerator
 FREIA has developed the prototype spoke RF source and validated the prototype
spoke cavity and, will validate spoke cryomodule, prototype high-beta elliptical
cavity with nominal RF power.
1)
Validation of high power RF amplifier (HPA)
2)
Validation of dressed spoke cavity
3)
Validation of cavity package
 Prototype cavity package (in test cryostat)
 Requires the availability of one high power RF amplifier tested during phase 1
4)
Validation of elliptical cavity package
5)
Validation of spoke prototype cryomodule
6)
Validation of prototype modulator and klystron
7)
Acceptance testing of series spoke cryomodules
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The Test Stand
 Four main subsystems needed
RF Power Station
Courtesy of P. Duthil
Cryogenics
Superconducting
cavity
Cryostat
Han Li 13th June 2017
LLRF
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Cryogenics
Helium liquefaction
 150 l/h at 4.5K (LN2 pre-cooling)
 2000 l LHe dewar/buffer, 3+1
outlets
 100 m3 gasbag + recovery system
 cryostats connected in closed loop
Liquid nitrogen
 20 m3 LN2 tank
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HNOSS Horizontal Cryostat
HNOSS: Horizontal Nugget for Operation of
Superconducting Systems
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Main Vacuum Vessel
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Valve box (on top of main vessel)
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Total volume ca. 7 m3
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Han Li 13th June 2017
LN2 and LHe
Cold gas heater for return flow
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Distributes cryogens to HNOSS and CM
Cryogenic transfer lines
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Distribute cryogens
4K and 2K pots, JT-valve, heat exchanger
5K supercritical helium
Magnetic shield (room temperature)
Thermal shield (LN2 temperature)
Interconnection box (ICB)
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3240 x ø1200mm inner volume
“beam” axis at 1600mm
Magnetic shield (room temperature)
Thermal shield (LN2 temperature)
re-heating from 2K to 300K
Subatmospheric pumps with cooling capacity of
90W at 1.8K
Control system
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RF Distribution
Main Hall
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Two 400kW RF Power Stations
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Main Bulk Outside Bunker
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Coaxial & Waveguide Lines
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Patch-Panels for Rearrangement
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Bunker
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352MHz RF Stations
 Dual Tetrodes Per Station
 400kW Peak at 14 Hz, 3.5ms
 Crowbar & Series Switches
 Two Stations Commissioned
 Station Efficiency Peak ~43%
Operating Point
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Circulators
 Thermal Detuning
 Thermal Oscillations
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704 MHz RF station
 Prototype modulator, lend by ESS
 Ampegon, 330 kW (for 2 klystrons)
 Commissioning with two dummy loads,
then attach klystron
 Prototype klystron, lend by ESS
 Toshiba type, 1.2 MW output power
 RF distribution, lend by ESS
 704 MHz waveguides, circulator and loads
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Solid State Amplifier
Single ended RF Power Amplifier (BLF188XR) tested in pulsed mode at 14 Hz and 3.5 ms
Individually: delivering up to 1500 W
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amplifier slightly modified on RO3003 for
series production
Max efficiency: 67% (pulsed)
Gain: 19 dB
Independent measurements at NXP
Two combined: Delivering up to 1700 W
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Max efficiency: 50% (1 dB IL in the output combiner)
Working on improving values
100 kW radial power combiner
output coupler connected to 3-1/8 inch coaxial line
30 mm
500 mm
7/16 inch input connector
1 kW level hot-S
parameter measurements
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The Self-excited Loop Test Stand (I)
 FREIA developed a test stand based on SEL for demonstrating the performance of
superconducting cavities both at low and high power, CW or pulse mode .
FREIA SEL block diagram for high power test
FREIA SEL block diagram for low power test
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The Self-excited Loop Test Stand (II)
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Combination with a DB RF station which can output up to 400 kW peak power.
Developed digital phase shifter and gain-controller.
Introduce interlock system for safety consideration.
Introduce RF switch in order to manage a pulse operation mode.
Developed SEL control and data acquisition system in LabView.
Interlock and RF switch
RF station
SEL loop installed into a cabinet
FPGA
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FREIA Labview SEL control system
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LLRF system from Lund University
Hardware
 Chassis: 12 slot µTCA, 1 kW power
supply
 MCH: NAT
 ADC and FPGA: Struck 8300-L2
 Vector modulator: DS8VM1
 Timing: MRF timing receiver
Useful features for the tests at FREIA
 Possibility to generate arbitrary RF pulses (no
feedback)
 RF signals monitoring with possibility to
generate an interlock signal
 Setting amplitude limit for the output RF signal
Software
 Direct sampling (undersampling)
of the RF signal
 Data acquisition and control
algorithms done in the FPGA
 High level control system: EPICS
 User Interface: Control System
Studio
Machine Protection and Safety Systems
Machine Protection
 Fast interlock: Compact Rio, NI cRIO-9024
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Cuts off RF signal. Fast digital 150 ns , some 10 – 20 µs
16 analogue channels (100 kHz) programmable thresholds.
300000 data points, post mortem
EPICS operator interface for set-up of RF interlocks.
 Slow interlock, S7-300 PLC system
 Currently about 100 i/o channels
NI cRIO-9024
Fast interlock
EPICS interface
Radiation protection bunker
 Bunker with clearing system
 Door switch trigger PLC and
 hardware interlock to RF
stations
Radiation area monitors:
Rotem Medismarts
Easily integrated with EPICS
FREIA bunker status display
 Dose rates
 Clearing status
 Warnings messages
 Graphs of dose rate
Oxygen deficiency detector
Tested Cavities
Hélène
 Three spoke cavities , Hélène, Germaine and Romea from IPN Orsay, have been
tested at low temperatures at FREIA.
Parameter
Helene (SSR)
Frequency [MHz]
360.4
Germaine and
Romea (DSR)
352.2
Beta_optimum
0.2
0.5
r/Q [Ohm]
117
427
Epk/Eacc
6.6
4.3
Bpk/Eacc [mT/MV/m]
13.4
89
6.8
130
Han Li 13th June 2017
Romea
Germaine
G [Ohm]
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Typical Measurements
 Low power:
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RF behaviour on warm cavity before installation in HNOSS,
Loaded Q-factor, eigen and external Q, Q0 = f(E) curve,
Lorentz detuning and microphonics,
Field emission onset and multipacting barriers,
Sensitivity to helium pressure fluctuations,
Residual resistance of cavity suface,
Cryogenic heat loads.
 High power:
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RF behaviour during cool down,
Coupler conditioning and cavity package conditioning,
Achieve nominal gradient and nominal Q0,
Cryogenic heat loads,
Loaded Q-factor, eigen and external Q, Q0 = f(E) curve,
Dynamic Lorentz detuning and mechanical modes,
Field emission onset and multipacting barriers,
Sensitivity to helium pressure fluctuations,
Tuning sensitiviy.
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Coupler conditioning (I)
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The warm and first cold RF processing was done using IPN Orsay’s system,
Followed by the new FREIA conditioning system to verify its performance,
All processes used a traditional signal generator driven loop,
The warm RF processing procedure took about 40 hours, while the cold processing took roughly 10 hours,
During warm conditioning, lots of outgassing occurred through the forward power region of 40-50 kW at
short pulses,
120 kW forward power was reached with 2.86 ms pulse duration at 14 Hz.
Forward power (W)
Time
Han Li 13th June 2017
One phase example of FPC warm conditioning
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Coupler conditioning (II)
 An automatic conditioning system, which consists of an acquisition system, a control system based
on LabView software and feedback was developed at FREIA.
 Key paremeters are primarily set.
Parameter
value
 The main devices for the RF conditioning process are:
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Loop control time (s)
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Signal Generator
Power Meter
Vacuum Gauge Controller (VGC)
Cold Cathode Gauges (CCG)
Arc Detector
Electron Detector
Fast RF Interlock Switch
Vacuum Pumping Cart
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Pulse repeat rate (Hz)
Vacuum upper limit (mbar)
14
1e-6
Vacuum lower limit (mbar)
Initial pulse length (µs)
pulse length step
5e-7
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20 µs, 50 µs,
100µs, 200 µs,
500 µs, 1 ms, 1.5 ms,
2 ms, 2.5 ms, 2.86 ms
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Cool down
 The cavity package in HNOSS cooled down from room temperature to 4K within 30 minutes,
 From 4K to 2K it took an extra 20 minutes,
 Cavity frequency was checking during cooldown.
200K to 4K
4K to 2K
Temp.
300 K
4K
2K
Resonance frequency
351.8939± 0.0001MHz
352.4004 ± 0.0001MHz
352.3725 ± 0.0001MHz
4.48 K/min
3.25 K/min
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4.10 K/min
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Cavity Package conditioning
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Cavity package conditioning was done by FREIA pulse SEL,
2.86 ms pulse with 14Hz repetition rate was used,
Cavity package conditioning took about 30 hours,
Three major multipacting regions have been found
 Forward power from 22 to 30 kW, peak gradient from 4.5 to 4.8 MV/m.
 Forward power form 35 to 48kW, peak gradient from 5.2 to 5.7 MV/m.
 Forward power form 67 to 76 kW, peak gradient from 7 to 7.5 MV/m.
Profile during MP
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Han Li 13th June 2017
The profile of cavity
voltage changes.
High radiation.
Accompany with
vacuum spikes.
Coupler temperature
increase.
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Static Heat Loads 20 mbar
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The cooling of the FPC was checked with Cernox sensors TT303 (inlet ScHe), TT305
(outlet ScHe) and a Pt100 sensor (TT147) connected to the midsection of the FPC.
P cavity
[mbar]
Eacc_peak
[MV/m]
TT303
[K]
TT147
[K]
TT305
[K]
20
0
14
39.5
291
20
9
9.8
41.6
278
TT303
(inside
HNOSS)
TT305
(outside
HNOSS)
At 20 mbar operating pressure, the static heat loads for
Romea with TT147 at ca 41 K amount to ca. 6.6 W
FT551
TT147
Identified four (4) regions depending on level
FT551
[m3/h]
7.12
6.81
6.54
6.11
Std dev
[m3/h]
0.34
0.31
0.33
0.33
LT101
min [%] max [%]
76
80
72
76
69
72
60
69
Note: tests where TT147 was varied between 30K
and 90K give an extra heat load of only 1W at 20
mbar.
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Q0 measurement (I)
 Calorimetrical measurement of Q0
 The level in the 2K tank was kept between 60% and 80%
 Close inlet and outlet valves of the cryomodule
 Record the pressure as a function of time for three (3) minutes
 Apply a known amount of resistive heat to the helium
 again record the pressure a function of time
LHe inlet
LHe outlet
Cavity
& 2K tank
Heater
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Pressure curve vs Applied Power
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Q0 measurement (II)
 Calorimetrical measurement of Q0 cont.
 Build the calibration curve: the rate of pressure rise vs. heat
 Load apply RF to the cavity and the system was left to stabilise only in pressure,
record the pressure rise
 Calculate the dynamic RF load using the calibration curve preliminary data
Pm = m*W+c
m = 0.0017
c = 0.015
Han Li 13th June 2017
Dissipate power calibration curve
Eacc_paek
(MV/m)
pressure
rise slop
dynamic RF load (W)
2,004499
2,515368
2,699868
3,02766
3,287095
3,591016
4,008444
0,0152
0,0153
0,0156
0,0158
0,0161
0,0162
0,0187
0,117647
0,176471
0,352941
0,470588
0,647059
0,705882
2,176471
4,317015
5,321938
5,966339
6,301396
6,589388
7,012012
7,360766
7,697375
8,07178
8,31318
8,659001
9,097229
0,0227
0,0359
0,0191
0,0185
0,0195
0,0245
0,0413
0,0432
0,0237
0,0252
0,028
0,0332
4,529412
12,29412
2,411765
2,058824
2,647059
5,588235
15,47059
16,58824
5,117647
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7,647059
10,70588
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Double Spoke Cavity Performance
(Romea, 2017)
 Test of cavity package.
preliminary data
ESS goal :
1.5×109
Han Li 13th June 2017
 Low-field Q0 factor of 1.4×109@ 2 K
 Q factor of 2,8×108@ Eacc_peak=9MV/m
 Several multipacting regions were found
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Dynamic Lorentz Force detuning (I)
 Monitoring and manipulating the complex signal from cavity during the pulse, dynamic
Lorentz force detuning at different gradient were studied.
preliminary data
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dVc
 1 / 2  j Vc  1 / 2 RL I
dt
r   r   1/2  sin    

 r   r1/2  1/2  cos    
state space equation
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Dynamic Lorentz Force detuning (II)
 Developed an FPGA-based LabView program for dynamic Lorentz force detuning.
 Frequency shift at peak accelerating gradient 9MV/m@ 2.86 ms pulse length is about 400Hz.
 A Loaded Q value of 1.8 × 105 from state space equation caculation is consist with the VNA
measurement.
preliminary data
∆𝑓 = 400𝐻𝑧
𝑄𝐿 = 1.8 × 105
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Mechanical Modes
 Stimulate the cavity by amplitude modulation .
 By sweeping the modulation frequency up to 800 Hz, the fit of mechanical modes was studied.
 Slow tuner is in fixed position .
preliminary data
Han Li 13th June 2017
Simulation from IPNO
N°
1&2
3&4
5&6
7
8 to 11
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Frequency
212 Hz
265 Hz & 275 Hz
285 Hz
313 Hz
315 Hz to 365 Hz
396 Hz
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Frequency Sensitivity to Pressure
 By closing both the inlet and outlet of the cryostat, checking the cavity frequency
increasing as a function of helium pressure from 20 to 40 mbar.
pressure sensitivity = +27.1 Hz/mbar
 This result is consistent with the 28 kHz frequency shift measured
during cool down from 4.2 K (~1030mbar) to 2 K (~20mbar).
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Tuner Sensitivity Measurements
 Slow tuner is controlled by Lund system.
 Tuning sensitivity:
150KHz/mm@2K
Length is defined by deformation of the cavity beam pipe.
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Test plan & Conclusions
 Test of Spoke Cryomodule and high-beta Elliptical cavity this year.
 Conclusions
 A test stand for high power test based on a self-excited loop was developed at
FREIA.
 The first prototype ESS spoke cavity package has been tested with the tetrode
based RF system.
 System is ready for Spoke Cryomodule.
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