COMET Task Force

COMET Task Force Report

7th J-PARC PAC meetingSatoshi MIHARAIPNS, KEK

COMET Task Force

Task Force

MembersS.Mihara, N.Saito, K.Yoshimura (KEK)M.Ieiri, K.Tanaka (KEK, Beam line experts)T.Ogitsu (KEK, SC magnet expert)A.Ando, K.Oide, M.Tomizawa (KEK, Acc experts)M.Aoki, A.Sato (Osaka Uni.)

Goal (defined by ourselves)In order to realize an experiment that can provide significant physics

result, the task force aims at showing a realistic solution(s) for theexperiment under discussions among experts from accelerator, beamchannel, and physics groups.

If possible a task force should be set up to consider the specialdemands of the required beam structure, energy, and intensity.Reports from these committees should be made to the PAC inupcoming meetings…. Minutes of the 4th PAC meeting

COMET Task Force

Tasks• Proton beam acceleration

– Investigation of the method described in the proposal– Other possibilities to produce required proton beam structure

• Extinction– 10-9 level necessary to reach 10-16 sensitivity– Development of measurement technique

• Proton beam extraction/transport– Proton beam transport to the target– Radiation shield around the target– Beam dump

• Experimental space– Possible location(s)

• In the current experimental hall• Extension of the current hall

COMET Task Force

Outline

•Proton Beam Acceleration

•Extinction Study Status

•Proton Beam Extraction/Transport

•Experimental Space

COMET Task Force

Proton Beam Acceleration

COMET Task Force

Proposed Method (I)• RCS: h=2 with one empty

bucket• MR:h=9 with 5 empty buckets• Bunched slow extraction

– Slow extraction with RF cavityON, 210kV

Realization of an empty bucket inRCS by using the chopper in Linac

•Simple solution

•No need of hardware modification

•Heavier heat load in the scraper

•Possible leakage of chopped beam inempty buckets

COMET Task Force

Proposed Method (II) & (III)

Space charge tune shift is half of (I)Longitudinal emittance is twice of (I)NO EMPTY BUCKET IN RCSRCS RF system needs minormodification (low level RF)

NO EMPTY BUCKET BOTH IN RCS ANDMRSpace charge tune shift is half of (1)LARGE MODIFICATION OF MR RFSYSTEM IS NECESSARYLong bunch

COMET Task Force

Proton Acceleration Prospect

•Try method (I) first for an extinctionstudy– No hardware modification is necessary– Investigate

•Time structure of the proton beam•(Heat load at chopper)•RF voltage while extraction

•Method (II) may be tested if h=1operation of RCS is realized for MRintensity upgrade– Check how extinction can be improved

COMET Task Force

MR Simulation• It will be useful to study the growth of beam

structure by a simplified simulation from theview point of “particle leakage from a bucket toanother”.

• FNAL Mike Syphers’s demonstration

•To simulate realsituation, we need tounderstand

•RF noise•Real shape(including the tail) ofthe beam in thephase space

COMET Task Force

Extinction Study

Extinction Study

•Extinction measurement usingsecondary beam

•Extinction measurement using a newabort line monitor

COMET Task Force

COMET Task Force

Measurement at K1.8BR• Measure secondary particle

time structure relative to areference signal from the MR– We need

• MR RF signal in theexperimental area

• Beam line hodoscope countersat the K1.8BR line

– Support by E15/E17 group• MR operation with empty

buckets• Bunched slow extraction

– Count the number ofsecondary particles as afunction of time

• Particle identification– TOF

• Integration for ~103 secondssupposing 1MHz counting rate

Delayed reference signals Counter signal

COMET Task Force

Abort Line Monitor• Utilize beam monitor in the abort line• Single bunch & single shot operation of the MR

– Look at the empty bucket before the filled one– Detector that can count the number of protons

• Two layers of hodoscopes– Plastic scintillator and quarts– Support by thin carbon fiber plates– Read by Multi-anode PMT through optical fibers– Operated in the beam line vacuum

COMET Task Force

Detector is Ready to Install• Cosmic-ray test OK• Evacuation test OK• Outgassing rate 10-5m3Pa/s

– Turbo pump near thedetector

COMET Task Force

Signal Quality Test• Need to transfer PMT signal

– from the abort line to thecounting room

– through 300m long cable• Very special cable

• Can we see PMT signal?– Tested using a normal

scintillation counter with PMTreadout

COMET Task Force

When beam is dumped…• Triggered by the abort line kicker excitation signal

– “Signal” seen ~20 µsec later and continued for 20µsec– Smaller pulses continued even after that for ~10msec

• No “signal” and No noise before that!

COMET Task Force

During acceleration• 180msec later after the start of acceleration• Clear correlation between “signal” and RF reference signal• Measurement using PMT is feasible to study time structure of the

primary proton beam

RF reference signal

COMET Task Force

Proton BeamExtraction/Transport

COMET Task Force

Bunched Slow Extraction

8GeV energyh=9, RF cavity ON, 210kVEL=3eVs, matched ellipse

Before extraction at ESS Extracted beam at ESS

70nsec

COMET Task Force

Effect of ESS foil• Example of simulation (done

for 50GeV study) usingMARS– 40cm downstream from ESS

exit

– “real loss”=N(hit p) –N(scattered p)/N=0.14%

– Remaining protons

– Scattered to extraction side

– Scattered to circulation side

• Need to redo the simulationfor J-PARC configuration

Scattered to extracted side

Scattered to circulating side

COMET Task Force

Beam optics calculation :TRANSPORT+G4Beamline

Proton Beam Transport

TRANSPORT

COMET Task Force

AC Dipole Section

B=600GB=0G

AC dipole Field

- G4Beamline• TRANSPORT

- G4Beamline• TRANSPORT

Optics Layout

COMET Task Force

Extinction Improvement•Extinction improvement >103

COMET Task Force

Experimental Space

COMET Task Force

Experimental Space

• Radiation– Difficult to move the target and dump after the

experiments completes

• Interference with other experiments– Day-1 experiments at K1.1 and K1.1BR– Primary beam experiments using B-line

• Electricity and cooling water– Power supplies for magnets– Refrigerator for the capture solenoid

COMET Task Force

A Possible Layout

COMET Task Force

Another Possible Layout

COMET Task Force

Power Supply and Refrigerator• At least two power supply units

of 5000-10000A 10V• 200W class He refrigerator

– cold box, dewar, compressor– He Buffer tank of 100m3

– LN2 storage• 80-100m2 for these

COMET Task Force

Summary

• Extinction tests– Abort line monitor measurement

– Detector is ready to install– Single bunch & single shot operation of MR

– Secondary beam line (K1.8BR) measurement– method (I) (5 empty and 4 filled buckets) operation with

bunched slow extraction• Need more simulation work for better

understanding of– possible leakage of beam during acceleration– extraction

• Layout of the experiment– Feedback from the COMET group