MTA RF Status01/31/ 2007

NF&MCC MeetingUCLA

A. Moretti

01/31/2007A. Moretti, NF&MCC Meeting, UCLA 2Fermilab

Purpose of the 805 and 201 MHz testing in the MTA

• The 805 MHz testing is a continuation of the 805 MHz testing conducted in Lab G with the addition of a 201 MHz test facility. The purpose being:

• Study Breakdown Limit of Vacuum Cavities.• Study Dark Current and X-Ray emissions at high

gradient• Study the effect of High Magnetic on Breakdown, Dark

Current and X-Ray emissions• Study Fast Muon Detectors in this environment.• Study in the Button cavity methods to reduce dark

current with different materials, coatings and processing using small insertable samples ( Buttons).

01/31/2007A. Moretti, NF&MCC Meeting, UCLA 3Fermilab

Description of the Experimental Setup

Linac Type Modulator and Controls• 12 MW 805 MHz Klystron system and 100 m Waveguide run and 5 MW 201 MHz system with 120 m 0.23 m Coaxial cable run.• Cavity High Vacuum System • Cavity cooling Water System• 5.0 T Solenoid• Support Cryogenic System• X-Ray Shielded Cave and X-Ray monitors Surrounding the cavity.• Interlocked RF with Sparking, Cavity Vacuum and External X-Ray level.• Clean room for preparing samples.

01/31/2007A. Moretti, NF&MCC Meeting, UCLA 4Fermilab

Experimental Layout

Detector

# 1

805 MHz Cavity

201 MHz Cavity

5 T Solenoid

2.73 m 1.38 m

Window

01/31/2007A. Moretti, NF&MCC Meeting, UCLA 5Fermilab

805 MHz Cavity under Test

• Testing Curved Be Windows coated with TiN.

• Flat windows were Freq unstable because of EM impulse.

• Frequency instability stopped by Eddy current brake in Magnetic Field.

• Curved window have been shown to be frequency stable without magnetic field.

01/31/2007A. Moretti, NF&MCC Meeting, UCLA 6Fermilab

Button Cavity to continue the 805 MHz Study with different Materials and Coatings.

Vacuumed Sealed Sample Holder

Sample Button Material

01/31/2007A. Moretti, NF&MCC Meeting, UCLA 7Fermilab

LBL 201 MHz

01/31/2007A. Moretti, NF&MCC Meeting, UCLA 8Fermilab

Picture of MTA Hall and 201 MHz Cavity

Current Picture of the MTA Hall showing the 5 T magnet in the foreground and the waveguide RF power input to 805 MHz cavity in back ground is the 201 MHz cavity.

201 MHz cavity during preparation for installation in Aug 05.

01/31/2007A. Moretti, NF&MCC Meeting, UCLA 9Fermilab

201 MHz 5 MW Amplifier and the 805 MHz 12 MW Klystron

201 MHz 5 MW Amplifier 805 MHz 12 MW Klystron System

01/31/2007A. Moretti, NF&MCC Meeting, UCLA 10Fermilab

First RF 805 MHz Commissioning without Magnetic Field Last March

Radation Mon.#1 vs Gradient

y = 3E-22x16.246

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Gradient in MV/m

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01/31/2007A. Moretti, NF&MCC Meeting, UCLA 11Fermilab

First Radiation Measurement with Magnetic Field compared to No Field Data

Rad Mon #1 vs Grad with 2.5 justa-positioned with no Field

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Grad mV/m

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Lines Without Magnetic Field

March 06, Results. Safe E Field Limit ~ 16 MV/m Detector Distance=1.34 m

01/31/2007A. Moretti, NF&MCC Meeting, UCLA 12Fermilab

Nov. 06 Results: Electric field limit at 2.5 T in the LBLSingle Cell Cavity with Curve Be Windows coated with TiN

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RF Commissioning with Mag Field at 2.5 T

Pre RF Commissioning without Mag Field

Nov. 06 Results:Safe E field Limit ~16 MV/mDetector Distance=2.73 m Acccounts for scale

01/31/2007A. Moretti, NF&MCC Meeting, UCLA 13Fermilab

Latest Electric field limit Data at 2.5 T and 1.25 T in the LBLSingle Cell Cavity with Curve Be Windows coated with TiN

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Gradient MV/m

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Asymptotic Gradient limit line at 1.25 T

2.5 T Data

RF Conditioning without Magnetic Field

The Asymptotic limit line shown indicates the continuous Gradient sparking limit. In all the cases studied including Lab G this line as predicted the Gradient Limit for the cases under Study.

For the 1.25 T case the Save operating limit has been shown to be

20 MV/m

1.25 T Data

01/31/2007A. Moretti, NF&MCC Meeting, UCLA 14Fermilab

Comparison of Lab G Results with the MTA Data

Safe Operating Gradient Limit vs Magnetic Field Level at Window for the three different

Coil modes

40403736

3432.431.73128.8

26.7426.425.922

404037.663535.2

3028.527.327

4040

25.7523.2522.521.520.9

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0 1 2 3 4 5Peak Magnectic Field in T at the Window

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tric

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(Solenoid)Yellow

(Opposing) Red

(Single Coil)Black Diamond

MTA Result ~ 16 MV/mMTA 1.25 T Result Jan. 07

01/31/2007A. Moretti, NF&MCC Meeting, UCLA 15Fermilab

CERN DC Spark Breakdown Compared to 805 MHz Cavity

History Of Breakdown Electric Field In a 1.25 T Solenoidal Field

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Spark Epoch Number

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Sparking History of 805 MHz Cavity

01/31/2007A. Moretti, NF&MCC Meeting, UCLA 16Fermilab

Conclusions and future plans

• Results of Lab G have been verified with the curved Be windows in March 06 and in Nov 06 at 805 MHz in the MTA at 2.5 T and In January 07 at 1.25 T.

• We need to continue the study to determine the mechanism for the enhancement of Dark Current in Large Magnetic fields: does it increase the number of emitters, the electric enhancement factor, or both?

• The button cavity will be used to study these and other questions: materials, coatings, etc. Plans are underway to install the Button cavity and begin these studies.

• Studies on the 201 MHz cavity are continuing and plans are underway to move it close to magnet to be in as high as fringe field as possible.