1. Notkestrasse 85, 22607 Hamburg, Germany
Parameter Set for High Duty Factor and CW Operation of a TTF-like Cryomodule; An Example*
Jacek Sekutowicz
DESY- MPY
Notkestrasse 85, Hamburg, Germany
* Work supported by EU under contract No (EUROFEL)
WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
Jacek Sekutowicz

2. WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
INTRODUCTION
In following I will talk on “Accelerating Unit”
The Unit consists of: One TTF-like Cryomodule (eight 9-cell sc cavities) +
RF-transmitter supplying the RF-power to all 8 cavities.
WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
Jacek Sekutowicz

3. WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
INTRODUCTION
General Remarks
CW and near-CW operation require low emittance SRF electron source
MHz) which does not exist at present
There are 3 improvements we need to make in the future for the cw or near-cw operation:
Increase intrinsic Q of sc cavities ► this lowers the cost of a cryogenic plant
Reduce microphonics ► this lowers the cost of a RF-system
Upgrade RF-source for cw or near-cw operation ► this also lowers cost of the RF-system
All three seem to be feasible.
WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
Jacek Sekutowicz

4. WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
ACCELERATING UNIT
Transmitter 2 x 60 kW
IOT
60 kW
Driver
380 W
Directional coupler
Load
Circulator
Quad.
38 kV
Power Supply
Based on EUROFEL DS5 Studies by the CPI Company
WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
Jacek Sekutowicz

5. WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
ACCELERATING UNIT
Transmitter kW
Quad.
IOT
120 kW
Driver
760 W
Directional coupler
Load
Circulator
47 kV
Based on EUROFEL DS5 Studies by the CPI Company
WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
Jacek Sekutowicz

6. WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
ACCELERATING UNIT
Assumption 1:
Cryogenic Dynamic Load 1.8 K
Max Pfor = 15.0 kW / cavity
Max Pin = 14.5 kW / cavity
Max Pbeam = 11.6 kW / cavity
Charge/Bunch: q = 1 nC
WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
Jacek Sekutowicz

7. WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
ACCELERATING UNIT
Assumption 2:
We will keep <cryogenic load> constant vs. Eacc
DF scales ~ 1/( Eacc)2
250 ms
Pfor
Pfor
15 kW
15 kW t 1s t
6 MV/m
12 MV/m
WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
Jacek Sekutowicz

8. WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
ACCELERATING UNIT
Assumption 3:
We will keep Pbeam constant vs. Eacc
Ibeam ~ 1/Eacc
q = 1nC stays constant but
tb ~ Eacc
q [nC] t 1
6 MV/m
tb= 0.54 µs t
12 MV/m
q [nC] 1
tb= 1.08 µs
WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
Jacek Sekutowicz

9. Dynamic cryogenic load 30 W/Unit at 1.8-2 K.
ACCELERATING UNIT
Assumptions Summary
Dynamic cryogenic load 30 W/Unit at K.
RF power transmitter supplies 120 kW/Unit.
20% of RF-power is reserved for the phase and amplitude stabilization.
3% RF-power is lost in the RF distribution system.
Single bunch has ~1 nC charge.
Table on the next slide contains data for the presented Unit and for
a XFEL-like linac with 120 Units.
WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
Jacek Sekutowicz

10. WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
ACCELERATING UNIT
Energy gain /Accelerating Unit
[MeV] 50 75
100
125
150
175
200
Eacc
[MV/m]
6.01
9.01
12.02
15.02
18.03
21.03
24.04 Qo
[1010]
2.0
Total Loss at 2K/cryomodule for DF = 100%
[W]
29.6
43.2
67.2
100.2
141.4
190.7
247.7
Duty Factor
[%]
69.4
44.6
29.9
21.2
15.7
12.1
Beam time
[ms]
1000
693
444
297
208
152
114
Pulse length
694
446
299
212
157
121
Beam current
[mA]
1.86
1.24
0.93
0.74
0.62
0.53
0.46
Bunch spacing when charge/bunch = 1nC
[µs]
0.54
0.81
1.08
1.35
1.62
1.89
2.16
Number of 1 nC bunches/s
[106]
1.855
0.857
0.412
0.220
0.129
0.081
0.053
Opt. Qext to keep power ≤ 14.5 kW/cavity
3.1
6.7 11 14 20 27 36
Max. allowed microphonics peak-peak
[Hz] 34 24 18
Total RF-peak power/cavity: beam + microphonics
[kW]
12.4
13.2
14.5
XFEL Energy for 116 acc. units
[GeV]
5.8
8.7
11.6
17.4
20.3
23.2
WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
Jacek Sekutowicz

11. WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
ACCELERATING UNIT
DF and Number of Bunches/s vs. Energy Gain
WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
Jacek Sekutowicz

12. WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
ACCELERATING UNIT
Power/cavity vs. Microphonics
WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
Jacek Sekutowicz

13. WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
ACCELERATING UNIT
Optimum Qext vs. Microphonics
WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
Jacek Sekutowicz

14. WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
ACCELERATING UNIT
The technical goals:
Intrinsic Q = 2∙1010 for Eacc in the range from MV/m.
Transmitter (IOT) delivering 120 kW.
Microphonics p-p < 24 Hz for nominal operation Eacc <18 MV/m and
< 14 Hz for the extended operation between 18–24 MV/m.
are feasible and can be reached in near future.
In case of technical difficulties:
Lower Q can be compensated with more cryogenic power or/and shorter pulses.
120 kW IOT can be replaced with 4 existing or 2 upgraded tubes.
Microphonics can be compensated with more RF-power.
WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
Jacek Sekutowicz

15. WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
CONCLUSIONS
Two basic assumptions
Dynamic cryogenic load of 30 W/Unit at K.
RF power of 120 kW.
led to operating parameter set for the 8-cavity cryomodule with one power source
allowing for acceleration of :
1nC bunches at Energy Gain 200 MeV/Unit (pulse = 121ms)
up to
1nC bunches at Energy Gain 50 MeV/Unit (cw)
with flexibility in the beam time structure resulting from the operation in cw or near-cw mode.
WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
Jacek Sekutowicz

16. WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
CONCLUSIONS: RF-SOURCE FOR CW OR NEAR-CW OPERATION
It seems at present that Inductive Output Tubes (IOT) could be very attractive
RF-sources for the cw or near-cw operation of linacs driving photon sources:
IOTs are very compact devices
Long life time (up to hours of operation)
Can operate in cw mode and pulse mode, with arbitrary pulse length
Do not take AC energy between pulses
Further development of IOTs should lead to higher output power
Higher output power (L-band 32 kW cw)
Higher gain (at present dB)
Higher overall efficiency (at present ~65%)
WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
Jacek Sekutowicz

17. WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
CONCLUSIONS: RF-SOURCE FOR CW OR NEAR-CW OPERATION
State-of-the-art IOTs
1.3 GHz IOTs
CPI
Pout [kW]
32 (85 pulse)
Gain [dB] 21
η [%]
> 65
WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
Jacek Sekutowicz

18. WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
CONCLUSIONS: RF-SOURCE FOR CW OR NEAR-CW OPERATION
CPI works on 60kW and 120 kW tube at 1300 MHz in the frame of EUROFEL studies
32 kW 1300 MHZ IOT
Preliminary parameters of 120 kW IOT (Modeling by H. Bohlen)
Parameter
Unit
Pout= 60 kW
(cw and pulse ok)
Pout= 120 kW
(pulse ok, cw?)
Voltage
[kV] 38 47
Current
[A]
2.5
3.7
Gain
[dB] 22
Efficiency
[%] 64
72.8
New R&D
Upgrade of the existing tube
Courtesy of CPI : H. Bohlen, Y. Li and P. Krzeminski
WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
Jacek Sekutowicz

19. Single Crystal 2.2 GHz Niobium Cavity
CONCLUSIONS: INTRINSIC Q OF SC CAVITIES
State-of-the-art Intrinsic Q
Single Crystal 2.2 GHz Niobium Cavity
Test #2: post-purification heat treatment at 1250 C for 10 hrs, 100 µm BCP, HPR
Courtesy P. Kneisel JLab
Courtesy P. Kneisel JLab
WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
Jacek Sekutowicz

20. WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
CONCLUSIONS: INTRINSIC Q OF SC CAVITIES
State-of-the-art Intrinsic Q
Courtesy P. Kneisel JLab
WG5: TTF Meeting, KEK, Tsukuba, September 25-28, 2006.
Jacek Sekutowicz