SRF results and requirements

Report
SRF Results and Requirements
cavities, coupler, tuner, HOM loads, & SC magnet
MLC Review
October 3, 2012
Matthias Liepe
1
One-Cavity Unit
Beamline HOM absorber
SRF cavity inside LHe tank
RF input coupler
Cavity frequency tuner
Matthias Liepe
2
SRF Cavity
Matthias Liepe
3
ERL Main Linac SRF Cavity
Static
Heat
Load
1.8 K
<1 W
Dynamic
Dynamic
Load
Load (worst
(average)
case)
11 W/cavity 44 W/cavity
Parameter
Accelerating mode
Fundamental frequency
Design gradient
Intrinsic quality factor
Loaded quality factor
Cavity half bandwidth at QL= 6.5107
Operating temperature
Number of cells
Active length
Cell-to-cell coupling (fundamental mode)
Iris diameter center cell / end cells
Beam tube diameter
Geometry factor (fundamental mode)
R/Q (fundamental mode)
Epeak/Eacc (fundamental mode)
Hpeak/Eacc (fundamental mode)
f/L
Lorentz-force detuning constant
Cavity longitudinal loss factor for σ=0.6mm,
non-fundamental
Cavity transverse loss factor for σ=0.6mm
Matthias Liepe
Value
TM010 
1300 MHz
16.2 MV/m
>21010
6.5107
10 Hz
1.8K
7
0.81 m
2.2%
36 mm / 36 mm
110 mm
270.7 Ohm
387 Ohm
2.06
41.96 Oe/(MV/m)
1.6 kHz/mm
~1.5 Hz / (MV/m)^2
13.1 V/pC
13.7 V/pC/m
4
Prototype Cavity Fabrication
Electron Beam
Welding
Quality control: CMM and frequency check
Finished main linac cavity with very tight (±0.25 mm) shape precision
 important for supporting high currents (avoid risk of trapped HOMs!)
Matthias Liepe
5
Full System Test of a 1-Cavity Main
Linac Unit in a Cryomodule
80K shield
HGRP
Gate valve HOM load
cavity
HOM load
First full main linac system test
• 1st test: cavity and tuner only
(completed)
• 2nd test: add high power RF input
coupler (under test)
• 3rd test: add HOM beamline loads
(next year)
Test cryomodule installed at Wilson Lab
Matthias Liepe
6
1st Cryomodule Test of ERL Main
Linac Cavity (with high Qext input coupler)
Cavity surface was prepared for high Q0 while keeping it as simple as possible: bulk
BCP, 650C outgassing, final BCP, 120C bake
Administrative limit. Cavity
can go to higher fields
Cavity exceeds ERL gradient and Q0
specifications: Q0=4 to 61010 at 1.6K in a
cryomodule!
Matthias Liepe
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Quality factor Q0
2nd Cryomodule Test of ERL Main
Linac Cavity (with RF input coupler)
Q0 ~ 2*1010 at 16 MV/m and 1.8 K
Eacc [MV/m]
Matthias Liepe
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High Q0 Results from Elsewhere
Average performance of eight
9-cell cavities in a FLASH
cryomodule at DESY
9-cell Cavity test in Horizontal
Test Cryostat at HZB
1.6K
1.8K
2K
Q0 ~ 2*1010 at 16 MV/m
and 1.8 K
Q0 > 2*1010 at 16 MV/m
and 1.8 K
Matthias Liepe
9
Alignment Results from the Injector
Cryomodule using fixed Supports
• High precision supports on cavities, HOM loads,
and HGRP for “self” alignment of beam line
– Rigid, stable support
– Shift of beamline during cool-down as predicted
X position [mm]
• Cavity string is aligned to 0.2 mm after cooldown! 1.00
0.50
X1 [mm]
0.00
-0.50
X3 [mm]
ERL Injector Cooldown
WPM Horizontal
X4 [mm]
X5 [mm]
-1.00
4/29/08 0:00
4/30/08 0:00
Date-Time
Matthias Liepe
5/1/08 0:00
5/2/08
0:00
10
MLC Requirements: Cavities
• RF performance:
– 16.2 MV/m (13 MV) average (5GeV from 384 cavities)
• 20 MV/m max (16 MeV) for overhead
– Q0 = 2*1010 on average at 16.2 MV/m (~11 W per cavity)
• Cryosystem should support individual cavities with Q0>5*109
• Cryosystem should support individual cryomodules with
Q0,avg= 1*1010
• Magnetic field at cavity location should be < 3 mG for Rres<1 nOhm
• Field stability (assuming non-correlated errors):
– Allowable relative amplitude error: (1 sigma) 6*10-3
– Allowable phase error: (1 sigma): 1 deg
Matthias Liepe
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MLC Requirements: Cavities
• Alignment:
– Cavities:
• Allowable transverse offset (x,y): (1 sigma) 2 mm
• Allowable pitch (1 sigma): 1.5 mrad (1.2 mm over
length of cavity)
– Quadrupole:
• Allowable transverse offset (x,y): (1 sigma): 1.6 mm
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Input Coupler
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Main Linac RF Input Coupler Design
Main Linac Input Coupler
Operating frequency
1.3 GHz
Maximum power (CW)
Qext (fixed)
Waveguide Flange
5 kW
Warm Ceramic Window
6.5×107
Air Cooling
300K Flange
40K Flange and cooling
Cavity
Flange
(1.8K)
Bellows
Instrumentation Port
Pump Port
Antenna
5K Intercept
Cold Ceramic Window
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14
Beamline: Input Coupler
•
•
•
•
2 kW average RF power
5 kW peak RF power
Fixed coupling
Large transverse flexibility (~1 cm
transverse motion during cool down)
• 5K and 40 – 80 K intercepts
Static Heat
Load
Dynamic Heat
Load
Full Heat Load
To 1.8K
0.05 W
0.06 W
0.11 W
To 5K
0.64 W
0.32 W
0.96 W
To 40K
3.78 W
5.94 W
9.72 W
Matthias Liepe
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Main Linac RF Input Coupler Prototype
and Test
• Prototype fabricated and tested successfully
• Tested up to full power specification of 5 kW CW
Matthias Liepe
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MLC Requirements: RF Input Coupler
• RF input coupler:
– 5kW peak
– 2 kW CW average
– Fixed coupling with Qext = 6.5*107
– >1 cm transverse flexibility for motion during cool
down
– Cryoloads per coupler: 0.1W at 1.8K, 1W at 5K,
10W at 40K
Matthias Liepe
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Frequency Tuner
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Design of Main Linac Cavity Frequency Tuner
Design optimized for CW cavity
operation with very high loaded quality
factor
• High stiffness
• Fast piezo actuators for fast
control of cavity frequency
Stepper motor for
slow control
Stresses at 26 kN tuner force
Piezoelectric actuators for fast control
Matthias Liepe
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Frequency Tuner
f [Hz]
f [Hz]
• Prototype tested successfully with prototype main linac cavity in test
cryomodule
500
100
0
• Excellent stiffness and linearity with 80
-500
0
100
200
very small hysteresis
60
Motor Steps - Injector Cavity
• >400 kHz slow tuning range
40
• 2 kHz fast piezo tuning range
20
0
0
Matthias Liepe
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40
60
80
Motor Steps - Main Linac Cavity
100
20
Microphonics Results From the HTC
and Elsewhere
4
Counts
80K shield
3
HGRP
Gate HOM load
valve
cavity
HOM load
x 10
Sigma = 4.6 Hz
Peak = 18 Hz
2
1
0
-20
Matthias Liepe
-10
0
f [Hz]
10
20
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MLC Requirements: Frequency Tuner
• Frequency tuner and microphonics:
– Slow tuner range: ~500 kHz
– Fast tuner range: >1 kHz
– Peak microphonics detuning: <20 Hz
• Sigma ~ 3.3 to 4 Hz (assuming peak = 5 to 6 sigma)
• Peak detuning counts (determines maximum RF
power)!
– 5 kW sufficient for 16.2 MV/m and 20 Hz detuning
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HOM Beamline Load
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HOM Beamline Absorber
40 to 80K intercept
Flange for
disassembly
5K intercept
Flange to
cavity
Shielded
bellow
• Broadband SiC absorber ring
• Full-circumference heat sink to
allow >500W dissipation @ 40K
• Includes bellow sections
• Flanges allow easy cleaning
• Zero-impedance beamline flanges
SiC absorber
ring brazed to
metal ring
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HOM Beamline Absorbers
Cavity at 1.8K
HOM load at 40 to 80K
Cavity at 1.8K
5K intercept
5K intercept
40 to 80K intercept
Matthias Liepe
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MLC Requirements: HOM Load
• Beam and HOM damping:
– Maximum beam current: 2 * 100 mA (ERL mode)
– Bunch charge: 77 pC
– Bunch length: 0.6 mm (2 ps)
– Longitudinal loss factor of cavity: 13.1 V/pC
– Average HOM power per cavity: 200 W at 40K
– Peak HOM power per cavity: >400 W at 40K
– Average HOM power per module: ~1.4 kW at 40K
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SC Magnet
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Superconducting Magnet
• One superconducting
quadrupole
• X-Y dipoles
• Cooled at 1.8 K
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MLC Requirements: SC Magnet
• Superconducting quadrupole
– Operating temperature: 1.8 K
– Maximum current: 110 A
– Maximum gradient: 19.4 T/m
Matthias Liepe
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The End
Matthias Liepe
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