1. V. Veshcherevich Cornell University
CORNELL ERL COUPLERS:
1. COUPLER FOR ERL MAIN LINAC
V. Veshcherevich
Cornell University
June 13, 2013
TTC Workshop 2013

2. ERL Main Linac Cavity
Each 7-cell cavity of the Cornell ERL Main Linac has one coupler
June 13, 2013
TTC Workshop 2013

3. RF power and Qext requirements10 6 7 8 9 2 4
RF power [W] Q L
0 Hz
10 Hz
20 Hz
30 Hz
40 Hz
7-cell cavity
@16.2 MV/m
RF power and Qext requirements are determined by microphonics (+ possible beam loss, beam return time errors, etc.)
June 13, 2013
TTC Workshop 2013

4. TTF-III Coupler as Prototype
The design of the ERL Main Linac coupler is based on the design of classic TTF-III input coupler
June 13, 2013
TTC Workshop 2013

5. Parameters of ERL Main Linac Coupler
Operating frequency
1.3 GHz
Maximum power (CW)
5 kW
Qext (fixed)
6.5×107
Cold coaxial line
impedance
70 Ohm
Warm coaxial line
46 Ohm
Cold coax line outer
diameter
40 mm
Warm coax line outer
62 mm
June 13, 2013
TTC Workshop 2013

6. Main Linac Coupler Challenges
Main challenges for the linac coupler:
Mechanical flexibility to accommodate large movement (> 10 mm) of cold mass inside the cryomodule during the cool down
Minimizing cryogenic heat loads
June 13, 2013
TTC Workshop 2013

7. ERL Main Linac Coupler Copper plating: 5μ Bellows Air Cooling
W650 Waveguide Flange
Cold Ceramic Window
Instrumentation Port
Pump Port
40K Flange
5K Intercept
Cavity
Flange
(2K)
Antenna
Warm Ceramic Window
300K Flange
Copper plating: 5μ
40K He Gas
Cooling
June 13, 2013
TTC Workshop 2013

8. Mechanical Flexibility
Coupler has great flexibility for accommodating large movement (> 10 mm) of cold mass inside the cryomodule during the cool down.
June 13, 2013
TTC Workshop 2013

9. ERL Main Linac Coupler: Main Parts
Cold Coupler
Air Cooling Socket
Waveguide Box
5K Cooling Unit
Warm Outer Conductor
Warm Inner Conductor
June 13, 2013
TTC Workshop 2013

10. Heat Load on Cryogenics
Heat Load for 5 kW of RF power
Static Heat Load
Dynamic Heat Load
Full Heat Load
To 2 K
0.05 W
0.06 W
0.11 W
To 5 K
0.64 W
0.32 W
0.96 W
To 40 K
3.78 W
5.94 W
9.72 W
June 13, 2013
TTC Workshop 2013

11. Coupler Test Stand Termination Cavity Ion Pump RF Power
from Transmitter
Coupler under Test
Termination Cavity
Ion Pump
Support Plate
June 13, 2013
TTC Workshop 2013

12. Coupler Performance Summary of the Main Linac coupler performance:
Two couplers have been fabricated by CPI, Beverly and tested at Cornell on the test stand up to 5 kW CW. No major issues were noticed during the test.
One coupler was attached to the prototype linac cavity. The cavity was successfully tested (w/o beam) with great results achieved inside the horizontal test cryomodule (HTC).
Five more couplers are ordered for the Main Linac Cryomodule (MLC) Prototype.
June 13, 2013
TTC Workshop 2013