1. Muon Facility at J-PARC Proton Driver Efficiency WS 29/Feb/2016
Naritoshi Kawamura
MUSE (Muon Science Establishment)
J-PARC/KEK

2. J-PARC
J-PARC consists of 3 accelerators (Linac, RCS, MR) and 3 experimental facilities (MLF, Hadron, Neutrino).

3. Muon Facilities in the world
ISIS
(pulse)
J-PARC
(pulse)
TRIUMF (CW)
PSI (CW)
Country
Japan
U.K.
Switzerland
Facility
J-PARC MUSE
RAL ISIS
PSI
proton energy [GeV]
3.0
0.8
0.59
proton intensity [MW]
1.0 (Goal)
0.16
1.3
m+ [/s] (surface)
3108 (U line)
6105
3107
m- [/s]
1107
7104
2107
CW / Pulse
Pulse (25Hz)
Pulse (50Hz) CW
50 GeV Synchrotron
(0.75 MW)
3 GeV Synchrotron
(25 Hz, 1MW)
Materials and Life Science
Experimental Facility
（Muon & Neutron)
Linac
(181MeV  400 MeV)
Pulsed muon beam don't need to mind about the pileup. No limit for proton beam intensity, but a highly segmented spectrometer is needed for mSR.

4. Materials and Life Science Facility
RCS (3GeV333mA)
MLF
Muon target
Spallation neutron target
Exp. Hall #1
Exp. Hall #2
Exp. Hall #1
Exp. Hall #2
High rad. area is isolated from the experimental halls
Beam transport tunnel

5. Materials and Life Science FacilityH S
Exp. Hall #1 H
40m
Muon production target S
Neutron spectrometers U D U
Neutron spallation target D
30m
Exp. Hall #2

6. Exp. hall #2 (West wing) U D U line: ultra slow muon
The world strongest muon beam is provided to generate ultra slow muon (USM).
USM microscopy opens a new research field of muon science. U D
U line
D line: decay muon
Momentum tunable (<120 MeV/c) m+ and m- beam meets a variety of users’ programs.
Constraction phase #1
D line

7. Kicker and septum was installed to provide muon beam both D1 and D2.
D-line
mSR spectrometer in D1
Kicker magnet
to D1
to D2 D1 D1 D2
Kicker and septum was installed to provide muon beam both D1 and D2. D2
Kicker Off
=double pulse
Kicker On
=single pulse
World record!

8. 20 times higher than D-line
U-line
SC curved solenoid
NC large aperture capture solenoid
3GeV proton
SC focusing solenoid w/ Wien filters
SC curved solenoid
212 kW
was observed in 2012.
20 times higher than D-line
All beamline magnets are axial focusing
Simultaneous extraction of m+ and m- beam
The world strongest pulsed muon: 3108 m+/s, 1107 m-/s

9. Generation of ultra slow muons
106 USM/s by 100 mJ/pulse 122-nm light

10. Exp. hall #1 (East wing) H S S line: surface muon
Surface muons are provided to many experimental areas simultaneously. H S
Extension of H-line for g-2/EDM exp.
H line: fundamental physics
Higher intensity tunable (<120MeV/c) m+ and m- beams are provided.
H line
S line

11. S-line S1 S2 S3 S4
Double-pulsed
Structure
40ms
25Hz
Port 2 S3 S1 S4
Kicker S2
Kicker
S line is dedicated to mSR studies, and provides muon beam to 4 experimental areas simultaneously.
At present, S1 area is completed.

12. H-line H-line: A beam line for fundamental physics
studies to search new physics beyond the SM.

13. Optics for H line +B -B 3GeV proton Capture solenoid (HS1)
30 MeV/c mono-chromatic beam calc. performed by a MC-code (G4beamline)
Large aperture short solenoids do not allow us to use transfer matrix calculation which use near axis assumption.
Bending magnet (HB1)
↑beam transport tunnel
Gate valve (HGV1)
Kicker magnets and/or wien filers are installable +B
Transport solenoid
(HS2 and HS3) -B
Septum or bending magnet (HB2)
Experimental area #1
Conceptual design was proposed by J. Doornbos, TRIUMF.
Experimental area #2 and #3

14. High rad. area around the target
4 secondary beamlines can be extracted.
D line: under common use, open for users
U line: under commissioning
S line: under commissioning
H line: only frontend magnets exist H S D
3GeV proton U
H line
Snapshot of maintenance floor 2.4-m high from the beamline
D line
Muon target P
S line
U line
M2 tunnel (beam transport tunnel)

15. Design concept of high rad. magnet
plug radiation shield
radiation-hard coil
level adjust spacer
seamless piping at beam line level
halo monitors
Utility connection at FL+4m level (maintenance floor)
phthalic paint
or Ni-plate

16. Muon production target
1/3 ISIS neutron target
Beam envelope
QN2
f70mm
Beam loss
QN3
QN4
The 2-cm graphite target causes a 5% (50 kW) beam loss mainly at target and scrapers.
Another 5% loss is reserved for the second muon target to be installed in M1.
The effect of radiation and the related things was well-studied for designing M2 devices.
>150W
QN1
Target &
Scrapers
Neutron target
5% loss
Transport efficiency

17. Fixed target Isotropic Graphite IG-430U (Toyo Tanso) Diameter: 70mm
Thickness: 20mm
P-Beam diameter; 16 mm (2s)
4kW 1MW proton beam
70 mm
20 mm
The 1st fixed target was used for 5 years since the 1st beam without replacement.
Duration of acc. operation: hours
Proton beam stop due to muon target: 3 hours (Water flow Low) ⇒ stable
Stainless steel pipe (Water)
Copper frame
Hot Iso-static Press method

18. Life time of muon target
The limit of target use will be 1 DPA. Target deformation is 1%.
DPA is expected to reach at 1 DPA after ½ ~ 1 year irradiation under 1MW.
Target replacement work consumes much money, time and human resources.
Development of the rotating target
Beam profile: uniform in p-space
DPA
Heat generation
Test of the radiation damage on graphite at PSI.

19. Rotating target
Referring to PSI, rotating target is adopted to distribute the radiation damage in graphite to a wider area.
Proton beam
Current fixed target
Rotating target
330 mm
The lifetime of graphite becomes long enough.
The lifetime of bearing determines the total one.
Solid lubricant in bearing:
Silver coating with MoS2 is selected in PSI's target.
Tungsten disulfide at MUSE. Expected lifetime: 10 years
Proton beam

20. Efficient muon facility
What is efficient muon beamline?
Large number of muons per proton.
Efficiency = muon production yield  capture and transmission efficiency
2  1015 proton/s (=1 MW)  5% is used muons/s in each 4 beam lines 10-6 m/p may be a conventional value.
New target material (SiC…) High capture and transmission efficiency by placing the solenoid just beside the target
Geometrical constraint Þ new target station

21. Summary
In MUSE, 4 beamlines are extracted, and they can answer a variety of users’ requests.
Typical value of 10-6 m/p is achieved. To improve this, new target station is needed.
However, from a different standpoint point Efficient facility: number of experiments to be conducted in a unit time is important. Furthermore, requested beam conditions by users have a variety, i.e. m+, m-, momentum...
For the next generation facility, we have to consider what is efficient facility.