K2K and JHF-nu muonmonitor
Jun Kameda (KEK)International workshop on Neutrino Beam
Instrumentation, Nov. 10, 2003 at KEK

1. K2K muon monitor
2. JHF-ν muon monitor
3. Summary

1. Muon monitor in K2K experiment

200 m
3.5m
Silicon detector

νμIon chamberπprotonπTargetz Purpose of the muon monitor:• Guaranteeing the beam direction spill by spill.
• We also use the muon monitor for beam tuning.

(Beam should be aimed to Super-K within 1 mrad in K2K).
•Indirect monitor of the horn magnet field and targeting.

1-1. K2K Muon Monitor
Ion Chamber
2 m x 2 m area iscovered.
32 ch. ( Y axis )36 ch. ( X axis )Silicon pad detectors
1cm x 2cm
PIN diode (x 17)
3.45cmx3.45cm PIN diode (x 9 )Two different typedetectors give aredundant monitoring1-2. Signal of the muon monitor
Ion Chamber

We can clearly see
the direction of thebeam.

Silicon Detector

1-3. Stability of the muon direction+- 1 mrad+- 1 mrad

Muon center is stable within ±1 mrad.

Super-KSuper-K

2. Muon monitors for JHF-ν
Purpose: • Monitor the beam direction spill by spill.
• Beam direction will be tuned using muon
monitor, so muon monitor is a key detector.
• Indirect monitor of the proton targeting position
and the horn magnet status.
Requirements:

1. Stability
Dead time of the muon monitors directly makes thedead time of the experiment.
(This is from our experience of K2K experiment.)
2. Good sensitivity for direction, yield & shape

3. Redundancy

2-1. Position of the muon monitor
Muon monitor will be placed behind the beam dump.
If the distance D become shorter,Æ Lower muon threshold, andthe sensitivity to the direction,
the horn magnet & proton
targeting become better.
Æ But, Higher radiation levelWe estimate a good D(m) by a Monte Carlo simulation.

2-2. Pμ distribution before the beam dumpz Muon yield has a good sensitivity for the Horn Magnet field.
z Over ~ 15 GeV/c muons don’t have the sensitivity tohorn magnet field.

2-3. Muon profile after propagating the beam dump
(projected to X axis )Beam dump( solid Fe is assumed )540 cmμ300 cm

D (cm)We can well see thecenter of the muon
beam with afew GeV/c thresholds.
Shape become wider
as threshold increases.
: All charged particles: muon+2-3. Muon profile after propagating the beam dump
(projected to Y axis )Beam dump( solid Fe is assumed )540 cmμ300 cm: All charged particles: muon+2-4. Sensitivity for the targeting position
Targeting position changes → Muon center moves.
Æ We can see the change of the targeting condition by muon.

proton beamtarget

3.0 cmhorn system works
as a Lens system2-4. Proton beam position vs Muon center∆(muon center)≈ 100∆(proton beam position)z Same order as K2K

measured value.
z Sensitivity is lower withhigher momentum
threshold (~ 7,8 GeV/c).

2-5. Particle flux at each depth
Muon flux:
6x107 muons /cm2/spill= 2.4x1014 muons/cm2/year
at 5 GeV/c threshold(=365 cm thick Fe)(same order as LHC)
electron flux:
1.2x107 particle/cm2/spill

5 GeV/c threshold

Simulation thresholds are set to:
proton, neutron : 2 MeV
γ,e+,e: 100 keV

2-6. Requirement for muon monitor in JHF-ν
1. Size:
Muon beam has about 1.0 m width (@ 5 GeV/c threshold).
Æ ~3 m x 3 m should be covered.

2. Muon momentum Threshold:Muon center is clearly seen with a few GeV/c threshold.
Around 3-5 GeV/c threshold, no big difference of thesensitivity of the proton beam position & magnetic field.

3. Radiation hardness:
It should survive much longer than 1 year
under 2.4x1014 muon/cm2/year condition at 5 GeV/cthreshold.

2-7. Possible detector types :Ion Chamber
Silicon detector

Diamond detector

CT ?

• Established technology.
It can work in this radiation level.
• Less radiation hard than diamonddetector, but a possible choice.
• LHC ATLAS uses Si detector
in the same order radiation level.
• Radiation hard than Si detector.
• We have no experiences, and we’ll
study in K2K beam.
• Directly measure muons aselectric current.
• Radiation hardness is expected to
be good, but work as a muon
monitor ?

Summary
1. K2K muon monitor:
muon monitor for K2K is working well, and the beam
direction is stable and aimed to Super-K within 1mrad.
2. JHF-ν muon monitor:
Requirement for the muon monitor is estimatedby Monte Carlo study:• 3 to ~5 GeV/c threshold give a good sensitivity for
proton beam position & horn magnet status.
• 6x107 muon/cm2/spill and 1.2x107 electrons/cm2/spill
are expected at 5GeV/c threshold.
(We should check with lower simulation thresholds,especially for neutrons.)

Plan• We’ll carry out beam tests using K2K beam (until 2005)¾ Radiation damage test of Si detector¾ R&D of the diamond detector• We’ll start design of the Ion Chamber.