3.9 ghz deflecting mode cavity timothy w. koeth july 12, 2005
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3.9 GHz Deflecting Mode Cavity
Timothy W. KoethJuly 12, 2005
Table of Contents
• History of 3.9 DMC • Cavity Simulations• HOM concerns and modeling • R/Q & it’s sensitivity to field flatness• Wake Field Simulations• Design: HOM couplers• Testing: Vertical Dewar Test Results• Status: ready to build !
Deflecing Mode Cavity History
The Deflecting Mode Cavity (DMC) was initially planned for use in the CKM, fixed target experiment’s beam line. When chosing a frequency, a multiple of the A0 facility was chosen as to provide a means of testing the cavity.
The cavity will provide a diagnostic to measure very short bunch length in the A0 Photo Injector.
Beam Line SimulationsFull 3-D E-M field made for 13 cell, polarized, model was generated in HFSS – a code that uses an adaptive mesh generating algorithim.
Uniformity map of the the integrated transverse kick along the the 13 cell cavity
The peak magnetic field along the cavity.
The electric field along axis is zero
HFSS generated a flat field distribution:
Beam Line SimulationsThe 3-D field map was used with the ASTRA code to understand the cavity’s effect
FW: 730 Femtosec
2.0 mm
Resolution: 10 to 20 fsec
Lower, Same, and Higher Order Mode Concerns
2000.00
4000.00
6000.00
8000.00
10000.00
12000.00
14000.00
16000.00
0 13.846 27.692 41.538 55.384 69.23 83.076 96.922 110.77 124.61 138.46 152.31 166.15 180
TM010 TM020 TM011 TMwierd TM021 TMwierd
TM031 TMwierd TM023 TM041 TMwierd TMwierd
Light Cone . . . .
0.00
2000.00
4000.00
6000.00
8000.00
10000.00
12000.00
14000.00
16000.00
0 13.846 27.692 41.538 55.384 69.23 83.076 96.922 110.77 124.61 138.46 152.31 166.15 180
m = 0 modes m = 1 modes
m = 2 modes not shown, but modeled.
Requirement: to be maintain the DMC in “standby” in the beam line at 4.5 K.
Will
Determination of R/QR (m)/Q in MAFIA for CKM 13 cell
1.0E-04
1.0E+00
1.0E+04
1.0E+08
1.0E+12
0 2000 4000 6000 8000 10000 12000 14000f (MHz)
R(m
)/
Q (
W/m
(2m
))
m=0 modes m=1 modes m=2 modes
R m
Q 1
r2m
2k m r
2
r2m
dz ˜ E zm r,z e i z / c
2
4U m
Problem modes:
to be filled in…
Tim
LOM, SOM, HOM Couplers
SAME ORDER MODE COUPLER
INPUT COUPLER
LOM & HOM CouplersWe are currently fine tuning the LOM and HOM coupler designs.
Attempting greatest 3.9000 GHz rejection – stay tuned !
LOM COUPLER
HOM COUPLER
SOM COUPLER
Wake Field Simulations
• Yet to be filled in….
- TIM
Vertical Dewar Test Results
RSURF vs TC/T
10.0
100.0
1000.0
10000.0
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
W
Preliminary 3-cell Result R BCS (Nominal, deltaT = 0)
Q vs PDEFL
1.0E+08
1.0E+09
1.0E+10
0 1 2 3 4 5 6 7 8
PT kick (MV/m)Run 1 Run 2 Design Goal
Preliminary
Cavity design parameters 13 cellsBMAX = 80 mT EMAX = 18.6 MV/mL EFF = 0.5 mP = 5 M V/m
Horizontal CryovesselFNAL already has a prototype horiztonal cryovessel that will host two 3.9 GHz cavities. With minor modification, we will retrofit for use in the Photo Injector Beam line.
Cryogenics Feed
Thermometry, LOM, SOM, & HOM power ports
RF input Coupler
DMC LLRF & HLRF
March 2005Established closed loop control of Fermilab’s A0 9-cell Superconducting cavity.
May 2005 Established remote control of SimCon setup at Fermilab
May 2005DESY’s remote control of 9-cell system.Closed loop remote control.Complete system calibration.Testing of Warsaw & DESY feed back algorithims
Established DESY-FNAL algorithm development collaboration
DESY LLRF Prep Tests at the FNPL A0PI:1st Display of SimCon2.1.0 closed loop control. A0, March 2005
Actual Field Amplitude
Programmed Amplitude
Prgrammed Phase
Measured Phase
Pic of 3.9 GHz Kly
here
DMC Status: Ready for final design production
December 2005: Cavity assemblies in construction
Summer 2006: Finish cavity production
Fall 2006 : Assembled cavity in cryovessel.
Winter/Spring 2007: Commision with beam