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

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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

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4000.00

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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