FLASH Toroid

• Review

• Progress since last meeting in April

• Next steps

• Summary

Johnny NgFLASH Coll. Mtg. 7/25/03

FLASH Toroid Electronics

Work done by Bob Simmons (SLAC BCS Group)

Specs: Sensitivity Range: 1E7 – 1E9 elec. Accuracy: 1% Calibrations via charge inj.:

•electronics only•toroid + electronics

Noise Achieved in lab: 1.5E5 elec.

(April 2003)

Test Toroid

Electronics Box

Bob’s Lab Bench

Progress since April Meeting

• Fabrication:– New toroid built;– Whole assembly installed on beamline

• Parasitic beam test in FFTB (June 2003)– Readout using FLASH DAQ (2249W ADC)– High current: basic operations, long term

stability– Low current: noise/sensitivity

FFTB Beam Line Map (Not to Scale)

“Green” Dump magnets

E165(Thin Target)

CollimatorPC 7.5

OD=1.2 inches

New Ion ChamberBeam Loss Monitor

beam

New FLASHToroid

OD=7/8 inches

Tunnel Entrance

High current beam test

Data set spans more than 24 hours

Excellent correlation with standard toroid: RMS ~ 0.2%

Charge injection calibration stable to 0.4% (RMS)

(current attenuator used to avoid saturation)

Low current beam test(current attenuator at front-end was still in place)

Excellent correlation with standard toroid down to N=5E9: RMS ~ 0.6%

Issues for N<5E9:Digitization noise in standard toroidSignal/noise in FLASH Lo-Gain mode.

FLASH Hi-Gain mode: RMS ~ 3%

The current attenuator was still in place for this test !!!

Low current special run

(current attenuator at front-end REMOVED - Run 507)

Signal clearly seen down to 2E7Pulse shape comparable to off-time calibration signalNo RF noise from beam !Detail features (“pre-shoot”?) need to compare 1-turn injection

Next Steps

• Absolute calibration in-situ– Network analyzer scans

– Pulse current measurements traceable to NIST

• Other tests– Linearity studies using pulser

– Calibration using 1-turn winding:

systematic effects?

• Useful RF techniques involved; could be a nice

project for a student.

NLCTA Beam Current Monitor Test Setup(C. Nantista, SLAC)

50 Matching

Center conducting rod

Calibration spool piece

Summary

• New FLASH toroid monitor and electronics for low-current built and tested successfully

• Some beam test results:– Excellent long-term stability

– No evidence of beam-related RF noise

– Clear sensitivity down to 2E7

• Next– Absolute calibration

– More systematic studies