FOUR YEARS OF SUCCESSFUL OPERATION AT THE EUXFEL - 2021 INTERNATIONAL CONFERENCE ON RF SUPERCONDUCTIVITY (SRF'21) - INDICO
←
→
Page content transcription
If your browser does not render page correctly, please read the page content below
Four years of successful operation at the EuXFEL 2021 International Conference on RF Superconductivity (SRF’21) Julien Branlard, for the EuXFEL Linac Operations Team Hamburg, 28.06.2021
Overview
2017 - 2021
Introduction – the EuXFEL Availability
• Layout • Monitoring
• Operating hours • Systematic trip review
• Max gradient experiment
Some key accelerator components • Detuning Cavities
• Gun
• AH1
• Klystrons Outlook
• Cryogenics • CW tests
• Long(er) flat tops
Linac Operation • MARWIN3
• Linac setup
• Cavities operation
• Dark current and field emitters
| 4 years of operations at EuXFEL | Julien Branlard, 28.06.2021 Page 2
The EuXFEL Accelerator
Facility layout
• Injector: Gun, A1, AH1
• L1: 1x RF stations (A2 = 4 cryomodules)
• L2: 3x RF stations (A3-A5 = 3x 4 cryomodules)
• L3: 21x RF stations (A6 – A25 = 21x 4 cryomodules)
Page 3
Introduction
XFEL : user facility
Milestones (some) Machine time (in hours)
• Dec. 2016 Cool down COVID-19
• Apr. 2017 First beam
• May 2017 First SASE Commissioning
• Sep. 2017 First users
• Jul. 2018 Max energy: 17.5 GeV
Early users
• Oct. 2018 3 SASE beamlines
• Nov 2018 Max bunch (2700)
• Jan. 2019 Parallel user run in all 3 beamlines
• Feb. 2020 30 keV photon energy
• May 2021 100% availability for 1 week
| 4 years of operations at EuXFEL | Julien Branlard, 28.06.2021 Page 4
SOME KEY ACCELERATOR COMPONENTS
Gun Operation NRF gun Parameter space and typical operation • NRF gun, 1 window, 10 MW klystron • 56 MV/m, ~ 6MW • RF flat top 600 usec max (typ. 560 usec) • Fast ramp up (
AH1
3.9 GHz
Parameter space and typical operation
• 8 SRF cavities, no piezo
• 80 kWpeak klystron (CPI)
• QL = 3.3e6 (3-stub tuners)
• Vector sum operation
Eacc = 5-7 MV/m / cav. Courtesy R. Jonas
Pk = 6.3 kW
• Pulse shape 750 usec fill + 650 usec flat
• dA/A = 0.02 % dP = 0.02 deg
• No incident over the last 4 years
• Very reliable operation
| 4 years of operations at EuXFEL | Julien Branlard, 28.06.2021 Page 7
HPRF
1.3 GHz 10 MW MBK klystrons
• Typically operated between 3 and 6 MW
Courtesy V. Vogel
• Early problems with cooling water pipes corrosion
(through radiation) now replaced
• In 4 years, 3 klystrons moved out of tunnel for
repair (2 water damage, 1 cathode)
• 1 week for complete klystron exchange
• On average 3 klystron events per week
(arcs, breakdown)
• On-going campaign to operate at minimal
modulator HV settings (85% from saturation)
• Klystron lifetime management to minimize down
time when break down
| 4 years of operations at EuXFEL | Julien Branlard, 28.06.2021 Page 8
Cryogenics
Performance and cold compressor XFEL RF shutdowns
• Initial cool down Dec. 2016 (2 weeks)
• Very stable cryogenic conditions Pdiss
He pressure = 30 mBar +/- 0.1 mBar
• Exchange cold compressor motors every He pressure
4 months as preventive maintenance
• Down time for complete cold motor exchange He flow
less than 36 hours Stable He level
and flow
• Dynamic heat load compensation via
heaters Heater power
Courtesy S. Barbanotti
Heater compensation
| 4 years of operations at EuXFEL | Julien Branlard, 28.06.2021 Page 9
LINAC OPERATION
Linac Setup
Two modes of operation:
• low-VS : for beam energies 11.0 – 14.0 GeV
• high-VS : for beam energies 14.5 – 16.5 GeV
High-VS (max gradient)
Energy overhead by placing Energy overhead by ramping
• Cavities operating at max gradient
all stations on crest all stations to max SP
more radiation coming from RF
• Cavities operating with almost no RF overhead
almost at quench limit
• Couplers, klystrons running with more power
more arcs, sparks, etc..
• Overall, operating on the edge
more trips
Page 11Cavity operation
776x 1.3 GHz TESLA cavities
Typical operation conditions
• Average gradient + spread
• Coupler power (x4 for peak power)
• Measured Q0 = 1 x 1010
Courtesy N. Walker
| 4 years of operations at EuXFEL | Julien Branlard, 28.06.2021 Page 12Cavity operation
776x 1.3 GHz TESLA cavities
Typical operation conditions RF regulation
• Detuning (+/- 18.5 Hz) • dA/A < 0.01 % (typ. 0.007 %)
Detuning Mean: 0 Hz
RMS spread: 18.5 Hz
• Loaded quality factor QL = (4.6 +/- 0.05) x 106 • dP < 0.01 deg. (typ. 0.007 deg.)
QL
Mean: 4.60 ×106
RMS spread: 0.05 ×106
Courtesy M. Omet
| 4 years of operations at EuXFEL | Julien Branlard, 28.06.2021 Page 13Dark Current Radiation in the Tunnel
Monitoring radiation
New field emitter detected (Sept. 2020)
RadFet RadCon MARWIN3
Administrative limit 500 uSv/h A12 operating
above its
operational
gradient
Position [m]
Page 14Field emitters
Example: A24.M2.C7 (Oct. 2019) and A18.M3.C4 (Sept. 2020)
A24.M2.C7
• Procedure
• Park MARWIN at peak neutron radiation (often located at quadrupole) sudden FE onset
observed by RadCon
• Detune / retune cavities one at a time until field emitter is found
• Once found, detune field emitter (30-40 kHz)
A18.M3.C4
administrative limit 500uSv/h
Page 15AVAILABILITY
Monitoring the RF Availability
XTL live report
GOOD week machine BAD week
study
few isolated short trips
pathological
2x
machine-level
trips
Page 17Systematic Trip Review
Closer look at availability since 2019
• Weekly review by linac ops team
• Review / tag the trips of the week
• Update database
• 8D review for trips > 4hrs down time
Clarify root cause
and update DB
Courtesy S. Köpfke
Page 18High-Voltage (high-VS) Experiment
• 31.08 – 18.10.2020 7 weeks at low-VS 6.3 SEU / week 56 SEU / week
70
SEU
• 19.10 – 22.11.2020 5 weeks at high-VS *
60
* Although the high-V linac configuration was only really needed for 1 user week 50
Total Low-VS High-VS 40
x6
30
Availability % 97.9 98.7 95.6
20
Total operation time days 125.2 90.4 34.8 10
Number of events 0
hrs 300 124 176
36 37 38 39 40 41 42 43 44 45 46 47
Total down time hrs 64.7 27.9 36.9 7
LLRF failures
6
Quenches
5
Total Low-VS High-VS Limiters x2-3
4
Trips hrs 40.1 13.5 26.6 3
Linac off (access) hrs 18.3 10.7 7.6 2
Ramp down hrs 3.5 1.8 1.7 1
0
Development hrs 1.9 0.8 0.8 36 37 38 39 40 41 42 43 44 45 46 47
Page 19Cavity Detuning Film credit : Nick Walker ®
To date 23 detuned cavities (out of 776x 1.3 GHz)
Nb. cav Reason Remark
4 Coupler over heating
1 Waveguide specification error known BEFORE tunnel installation
4 Excessive field emission or too low quench Eacc
1 Excessive dynamic heat loss Soft quenching ?
12 – 2 Maximum gradient investigation (w/o piezo) 2 were retuned since. Possibly more to come
3 (New?) field emitters 1 is clearly new; the other 2 unclear.
Emergency Detune
• First triggered in 2020 due to COVID-19
• Unclear if staff on-site could guarantee cryo operation
• Manually detune all 784 SRF cavities (16 hours)
• Developed a “1-button” emergency detuning tool (45 mins)
Notes:
• does not track the cavity detuning (only motor steps) • A17 had been previously detuned to test the tool
• A9 motor driver failure (cryomodule 1 & 2)
• runs / tracks all 52 motor drivers in parallel • Cavities “normally” detuned stay detuned
• Needed in unlikely case of uncontrolled warm-up
| 4 years of operations at EuXFEL | Julien Branlard, 28.06.2021 Page 20Outlook
Some short- to mid-term goals
• Maintain and keep pushing toward higher availability
• Automation
• System health
• Support from machine learning and AI
• R&D for a CW upgrade of the EuXFEL
• RF control challenge: CW in vector sum
150 usec 750 usec 650 usec 50 usec
• R&D to extend RF flat top w/o changing infrastructure
• Explore QL and fill time parameter space
• Use fill and fall time of modulator pulse
| 4 years of operations at EuXFEL | Julien Branlard, 28.06.2021 Page 21Thank you
Courtesy A. Dehne
Special thanks to my colleagues for their help gathering the
material for this talk:
Valeri Ayvazyan, Serena Barbanotti, Frank Brinker, Stefan
Choroba, Marie Czwalinna, Winfried Decking, Andre Gössel,
Rolf Jonas, Siegfried Köpke, Björn Lautenschlager, Manuel
Mommertz, Sven Pfeiffer, Christian Schmidt, Tobias Schnautz,
Matthias Scholz and Nick Walker
Contact
MARWIN1 MARWIN2 MARWIN3
Deutsches Julien Branlard
Elektronen-Synchrotron MSK
Julien.branlard@desy.de
www.desy.de +49 (0)40 8998 1599You can also read
