rf upgrades & experience at jlab
DESCRIPTION
RF Upgrades & Experience At JLab. Rick Nelson. Outline. Background: CEBAF / Jefferson Lab History, upgrade requirements & decisions Progress & problems along the way Present status Future directions & concerns. CEBAF at Jefferson Lab. Design 4 GeV, 200 uA 3 Experimental Halls - PowerPoint PPT PresentationTRANSCRIPT
CWRF2014 May 13-16, 2014
RF Upgrades & Experience At JLab
Rick Nelson
CWRF2014 May 13-16, 2014
Outline
• Background: CEBAF / Jefferson Lab• History, upgrade requirements & decisions• Progress & problems along the way• Present status• Future directions & concerns
CWRF2014 May 13-16, 2014
CEBAF at Jefferson Lab• Design
– 4 GeV, 200 uA• 3 Experimental Halls
• Present (pre-upgrade)– 6 GeV, 200 uA
• 3 Experimental Halls• Upgrade
– 11 GeV, 200 uA• 3 Experimental Halls
– 12 GeV, 200 uA• 4th Hall D only
CWRF2014 May 13-16, 2014
CHL-2
Upgrade magnets and power supplies
Upgrade Existing Halls
From 6 to 12 GeV
CWRF2014 May 13-16, 2014
RF + Upgrades
• Original– 42.5 cryomodules/338 SC cavities – 340 klystrons: 5 to 6.5 kW CW, 1497 MHz
• Incremental upgrades to C50 ongoing• C25, C50 cryomodules
• Upgrade– 10 cryomodules, 80 SC cavities– 80 klystrons: 13 kW CW, 1497 MHz
• New designs for klystrons, power supplies, circulators, controls
CWRF2014 May 13-16, 2014
Key RF Requirements 10 new zones of RF power for new accelerating structures:
•1497 MHz•Operating Gradients Required• >17.5 MV/m
•RF Power per cavity•13 kW saturated
•Regulation requirements•(table)
•Cavity QL• ≥ 2x107
Superconducting Cavity
8
High Voltage Power Supply
Klystron
LLRFControls
EPICS IOCEthernet
Ethernet
MasterOscillator
Fast ( <1sec)
Slow (>1sec)
Phase Stability
(rms)0.5º 3.0º
Amplitude(rms) 4.5x10-4 NA
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
-600 -500 -400 -300 -200 -100 0
Detuning (Hz)
Ener
gy C
onte
nt (N
orm
.)
Cavity de-tuning curve
CWRF2014 May 13-16, 2014
1 per cavity (existing configuration)Minimum impact of failures
1 per zone or 1 per linacLarger impact on faultsHigh power splittersHigh power amplitude and phase control required with high precision.
Additional controls and high power modulators found to be more $$ than individual RF sources.
How Many RF Sources?
Single LINAC upgrade shown
CWRF2014 May 13-16, 2014
Parameter Old Spec
New Spec
Actual Units
Power 5 to 8 13 13 KW
Center frequency 1497 1497 1497 MHzBandwidth, -1dB 5 5 5+ MHzBandwidth, -3 dB 6 6 6+ MHz0.5 dB incremental gain at 4 10 meets kWEfficiency (at rated power) 32 >50 50.9 %Gain 38 >42 >50 dBHarmonics -20 -20 meets dBcBeam voltage 11.6 <16 14.5 kV DCHeater voltage 7.3 7.3 7.0 typ V DCModulating anode Yes Yes YesIsolated collector Yes Yes YesCavities/Resonators 4 5 5Focus PM EM ~900 Watts
CEBAF Klystrons Compared
CWRF2014 May 13-16, 2014
• Each system powers 8 klystrons (as before) • Resonant mode switcher design (15-20 KHz)• 4 separate supplies. Each feeds 2 klystrons
– Minimizes klystrons taken offline due to power supply failure
– Controlled as a “unit”• Each adjustable to -15kV • 15 A total• Design adapted from electrostatic
precipitator application (higher volts/lower amps & in oil) 1000+ units in the field at award
• Highly tolerant to load faults• Lower stored energy than T-R, fast
turn off on fault, series resistor limits output current (no crowbar)
HV DC Power Supply
CWRF2014 May 13-16, 2014
Additional Views
Rear View
HV Deck (4 per system, on rollers)
CWRF2014 May 13-16, 2014
Typical RF Installation
All zones installed and commissioned with beam
CWRF2014 May 13-16, 2014
Tunnel Connections
Waveguide installation
CWRF2014 May 13-16, 2014
RF Commissioning Selected Data
Zone/Cavity Gradient Cryomodule
Energy GainBeam
CurrentZone/Cavity Gradient Cryomodule
Energy GainBeam
Current
SL24 SL231 15 100 1 20.4 NA2 13.9 100 2 18.4 NA3 13.4 100 3 19.4 NA4 15.4 100 4 18 NA5 19 100 5 21.4 NA6 20 100 6 20.6 NA7 17.7 100 7 22.2 NA8 14.7 100 8 15.8 NA
Total 129.1 90.37 100 Total 156.2 109.34
SL25 SL221 19.5 465 1 12 NA2 20.5 465 2 21.2 NA3 18.7 465 3 18.5 NA4 20.5 465 4 20.2 NA5 19 465 5 18.7 NA6 20.1 465 6 20.7 NA7 17.5 465 7 20.2 NA8 18.5 465 8 20 NA
Total 154.3 108.01 Total 151.5 106.05
Commissioned w/ Beam Commissioned w/o Beam
CWRF2014 May 13-16, 2014
Good Times / Bad Times• Everything according to plan?• Delivery delays on several key components
• Klystron & general WG close to schedule with no problems• HOM filters, isolators, solenoid power
– Revisions and rework for problem areas– One contract cancellation– Multiple installation delays with starts & stops
• Largely from budget constraints• Resulting in reassignment of workforce• Inefficient to change tasks to often
CWRF2014 May 13-16, 2014
Isolator Requirements• 13 kW CW, full reflection• 0.2 dB insertion loss• 21 dB isolation (any phase & power)• Water cooled• PM only - no TCU • Operates adjacent to others• Awarded to Ferrite (also supplied 350+ units for original
CEBAF)• Full power testing at JLab
– Vendor test capabilities missing– Several rounds of testing with sliding short
• Using FA klystron at L-3• At JLab using 2 x 6.5 kW and 13 kW klystron
CWRF2014 May 13-16, 2014
Events
• Initial tests looked OK and first lots were installed• Tests into WG shorts not as good• Results not repeatable/consistent with similar test
connditons• And, performance varied based on phasing (Distance
to short)– Two rounds of measurements & adjustments to
understand the fix– Tried to characterize performance and make
adjustments before next production batch– Next production units still variable
CWRF2014 May 13-16, 2014
Testing
CWRF2014 May 13-16, 2014
Sensitive to Match & Phase• Isolation affected by
– Ferrite temperature– Magnetic field strength
• Could be adjusted to maintain good performance• Less field needed at higher temperature• Other solutions include TCU, active field control
(VSWR)• “Automatically” handled in small units
– Reflected phase– Match (all ports)
• 2 of 3 need to be good for high isolation• Load OK, short bad, klystron needs to be good (but
not easily measured)
CWRF2014 May 13-16, 2014
Early Test Results
0 2 4 6 8 10 1210
15
20
25
30
35
11.5" short iso
Iso-J1223 11.5"Iso-J1196Iso-J1204iso 1210iso 1229Iso-J1219Iso-J1217-10"Iso-J1217-11.5"Iso-J1199-11.5"Iso-J1209-10"Iso-J1209-11.5"
CWRF2014 May 13-16, 2014
Early Test Results
CWRF2014 May 13-16, 2014
Isolation vs. Short Position
0 1 2 3 4 5 6 7 8 9 10 11 1210
15
20
25
30
35
40
Iso-J1612-11"Iso-8.5"Iso-10"
Forward Power (kW)
Isola
tion
(dB)
CWRF2014 May 13-16, 2014
Temperature• Initial measurements done steady-state
– Find position for lowest isolation (worst case, run plots)
• Changes then observed at turn-on– Concerns for off-resonance conditions at turn-
on• Must avoid tripping on high reflected
power at turn-on• Must work under varying conditions due to
differing distances to cavities
CWRF2014 May 13-16, 2014
Isolation vs. Heating/Time
00:00.0 00:08.6 00:17.3 00:25.9 00:34.6 00:43.2 00:51.8 01:00.5 01:09.140
45
50
55
60
65
70
75
15
17
19
21
23
25
27
forward-0reverse-0isolation-0
Elapsed time (seconds)
pow
er (d
Bm)
• RF heating of ferrite resulted in significant changes over (short) time
CWRF2014 May 13-16, 2014
Adjusting Magnetic Fields
00:00.0 00:08.6 00:17.3 00:25.9 00:34.6 00:43.2 00:51.8 01:00.5 01:09.110
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Isolation response at 10+ kW vs Magnet Count
isolation-0isolation-1isolation-2Isolation-3isolation-4
CWRF2014 May 13-16, 2014
Isolator
CWRF2014 May 13-16, 2014
Tuning
CWRF2014 May 13-16, 2014
Resolution• Vendor reworked dome – new domes, improved
cooling, full rebuild all units• … results were still variable• LL tuning abandoned in favor of full power setup at JLab
– 100% re-tested at power • Some adjustment to requirements allowed – lower isolation at
lower power• Reflected power well below threshold for klystron damage or
performance degradation• Final solution meets operational needs including credible fault
conditions• All 84 units modified, tested, reinstalled• Considerable extra work -- all units were handle multiple
times installed/removed/reinstalled.
CWRF2014 May 13-16, 2014
Isolation vs. Short Position
7 8 9 10 11 12 130
5
10
15
20
25
30
35
Iso-J1612
Iso-J1612
Short Position (inches)
Isola
tion
(dB)
CWRF2014 May 13-16, 2014
HOM Filters– Uncertainty of need, though requirements known– Originally not needed, later added back in– Belief was only 2 of 8 cavities would require HOM filter– Normal procurement process
• 2 vendor offers• Final units essentially identical to what we had from
multiple purchases– Performance met, cost lower though alternate proposal was more
robust• Small tweaks to reduce fundamental absorption• Manufacturing relied on external shops (as before)
– Vendor a small concern, limited resources & staff– Fabrication subcontracted (metal fab, Iridite, dip brazing)
• Dummy spool pieces installed in other positions• Had expected this to come in last
CWRF2014 May 13-16, 2014
Klystron HV PS• Performance has been good overall
– Switcher design and controls work well - good reliability• DSP-based controls with hardware safety interlocks• Code changes needed to address timing issues
– 1 unit tested OK, but all 4 might trip external breaker– Extended step-start to deal with high inrush & breaker trips
• Possible race condition for contactor control vs. status reporting (several contactors changed but seem to be OK)
– Control transformers (480:120) shorted out– Loose connections/loosening connections
• Contactors, IGBT– Suggestion: check connections…
• No similar problems with old supplies, but a lot less connections– DC power guys regularly check transistor connections
• New doesn’t mean perfect -- especially after x-country trips• A couple noticeable events
CWRF2014 May 13-16, 2014
Flash, Boom – Tripped 3 Breakers
CWRF2014 May 13-16, 2014
Cause & Effect
CWRF2014 May 13-16, 2014
IGBT Connection• Another loose
connection• IGBT overheating &
short circuit• Checked torque on all
connections, all systems
• No early signs noted – just tripped
CWRF2014 May 13-16, 2014
Problem Procurements• Isolator (discussed)• HOM filter (discussed)• Klystron solenoid PS
– Offer looked good on paper• Major design effort resulted in delays and
cancellation– FA looked like a lab prototype – and didn’t work
long– Test results failed to meet their results (tried 3
ways)– Ultimately cancelled and purchased from Sorensen
CWRF2014 May 13-16, 2014
We Didn’t Buy This One
• Liberal use of RTV to insure components didn’t shift during shipping…
• Kluge board• Not First Article class• Order cancelled
CWRF2014 May 13-16, 2014
Installation Challenges• Funding shortages resulted in work
reassignments & delays• Techs reassigned to dismantle other
systems(multi-month delays)• Start/stop/start not efficient and required
relearning• (In spite of this RF finished on time and
below budget)
CWRF2014 May 13-16, 2014
A Wet Year• Brazing issues and water leaks
– Multiple new components, nuisance problems– Both believed to be of similar origin – but
different suppliers– Pressure tested (but not long enough)– Trapped flux dissolved out resulted in small
leaks on a few pieces• Circulator load assemblies
– New loads built, and testing refined• Solenoid leaks on plumbing
– Longer pressure testing with hot water
CWRF2014 May 13-16, 2014
Ongoing Circulator (old style)• Reliable for a lot of years,
but load failures becoming more frequent
• LC DI water• 15 years+ erosion and
leaching• Self-rebuilding w/o
retuning – Same load back to its
circulator• New circulator loads
won’t experience this failure mode
CWRF2014 May 13-16, 2014
Water Flows Downhill• All LCW was turned off during extended down
(~1 year)• Circulator load seals lost their seal• Water in select waveguides (not our selection)• HOM filters soaked
Water level – horizontal run
Bleed hole was for air…
CWRF2014 May 13-16, 2014
Maintenance Issues
• New systems to be learned and maintained
• New systems to be re-checked• Old systems getting older• Spares needed for new (and old alike)• Major PM efforts planned for summer
– Pushed off many times already
CWRF2014 May 13-16, 2014
20 Year Old Transformers
CWRF2014 May 13-16, 2014
Summary• All new LINAC RF has been installed and
commissioned, though not without issues along the way
• Operating requirements met• Staff still learning operational
maintenance differences from old systems• Maintenance activities scheduled for
summer down – old and new systems• Lobby to purchase spares with new
equipment
CWRF2014 May 13-16, 2014
12 GeV Timeline• 2009 12GeV Upgrade construction starts in May with ground breaking
ceremony at the Hall-D site.• 2011 First C100 installed in the 2L23 slot in CEBAF, July.• 2012 C100 module successfully operated at design specifications: 108MeV
of energy gain with 465μ A of beam loading on May-18.• 2013 North and South Linac 2K LHe operations established, Dec-09 for the
first time with two CHL's plants connected to a "split CEBAF".• 2013 12GeV CEBAF Beam Commissioning begins Dec-13.• 2014 Beam successfully transported to the 2R dumplette with 2.2GeV/pass
energy gain on Feb-05. Establishing RF capability to support 12GeV 5.5pass operation with greater than 50% availability.
• 2014 Injector achieves 12GeV design energy of 123MeV on Mar-10• 2014 3-pass beam established to Hall-A Mar-20. Multi-pass capability
established in the 12GeV era. • 2014 3-pass beam with E>6GeV established to Hall-A on Apr-01 and
beam-target interactions recorded. First time beam transported to an end-station with energy that exceeds maximum energy set during the 6GeV CEBAF era.
• 2014 10.5GeV 5.5 pass beam established to Hall-D Tagger dump on May-07.
• 2014 First RF separated beams in 12GeV era on Oct-??. Establishes multi-beam capability in the 12GeV era.
CWRF2014 May 13-16, 2014
Thank You!