1. Beam line Experiment area SC magnet Pion production target
COMET Facility
Beam line
Experiment area
SC magnet
Pion production target

2. Construction of high-p/COMET beam lines
Beamline magnets
Dx7, Qx8
Steel-septum (Lambertson) magnet,
Current-septum magnets x2
Collimators
(H, V)
小沢の発表に含まれている
3 of existing beamline magnets
(Dx1, Qx2) are replaced to avoid interference with new line
Most of beamline magnets
(Dx7, Qx6) are reused ones
vertically steering magnets (x2) to make a bump orbit for beam extraction to high-p/COMET
Installation in SY has started

3. Construction of high-p/COMET beam lines
Beam plugs
High-p beamline magnets
Dx5, Qx3 FM
Beam plugs
high-p
beam dump
COMET beamline magnets
Dx5, Qx4
小沢の発表に含まれている
COMET
beam dump
Capture Solenoid
Most of beamline magnets
(Dx8, Qx5) are reused ones
Installation in Hall will start next JFY

4. Top View of the Branching Point from A-line
Steel-Septum
(Lambertson)
Magnet
Current-Septum
Magnet
existing beam line
high-p/COMET
beam line
小沢の発表に含まれている
5° in total

5. Steel-Septum (Lambertson) Magnet
yoke
vacuum chamber
coil
小沢の発表に含まれている
bending field
field free hole
proton beam

6. Operation Modes at Branching Point
10-4 protons
小沢の発表に含まれている T1
T1 + High-p
COMET
all protons are
delivered to T1 target
10-4 protons are
branched into
high-p/COMET line
all protons are
bent into
high-p/COMET line
vertical beam position at BP is adjustable using 2 steering magnets

7. COMET Hall : B1F Plane View

8. COMET Hall : B1F Plane View
Machine
Room
Beam Room
小沢の発表に含まれている
Beam
Dump
Exp. Room

9. COMET Hall : Section View
Control Room
Installation Yard
Machine
Room
小沢の発表に含まれている
Exp. Room
Beam Room

10. Radiation Evaluation Radiation level around the COMET building
was evaluated using MARS simulation.
2.6
mSv/h
0.7
0.05
2.6
mSv/h
(#167)
0.05
mSv/h
(#100)
0.7
mSv/h
(#135)
Each Box in the left figure corresponds
to each point in right plot.
Radiation contamination of the soil is estimated to be smaller than
the limitation of 11 mSv/h.

11. Radioactivation of Air / Water
Radioactivation of air in the beam room / experimental room and
cooling water after 90-days operation was evaluated based on MARS.
Half
Life
Air
Beam room
(Bq/cc)
Exp. Room
Air Evacuation
Limit
Water
Drain 3H
12.26y
3.1E+00
7.07E-03
5.0E-03
542 60
7Be
53.4d
2.3E+00
7.32E-03
2.0E-03
1408 30
15O
2.04m
6.0E+01
1.00E-01
7.0E-04
180567 5
13N
9.97m
8.1E+01
2.01E-01
2558
11C
20.4m
5.1E+00
2.00E-02
5113
0.1
41Ar
1.85h
3.7E+01
4.81E-01
5.0E-04 NA
施設としてはかなり重要ですがかなり細かいので説明も大変。飛ばしても問題無いと思います。質問が出れば私か深尾くんが説明します。
- Radioactive nuclide density in air exceeds evacuation limit.
Both beam room and experimental room are air-sealed during
beam operation.
- Radioactive nuclide density in cooling water exceeds drain limit.
7Be is collected by filter. Short-life nuclides density is sufficiently
reduced in 1 day. 3H must be drained after diluting.

12. Air ventilation diagram of the COMET Hall
重要ではないですが、ちゃんと設計してますという状況説明のみ。一次ビームラインは放射性物質が漏れた際もファルタ−通して排気できるように設計されています。

13. Superconducting Magnet
Iron Yoke
Tungsten
Shield
Proton
Target
8GeV proton m
6.4m
Status of SC Mag. Production:
Engineering design of SC coils
has been initiated
Procurement of superconducting cable was started. 5T
吉田君スライド。まだ設計段階で写真はないです。
Pion Capture
Solenoid
Transport 3T
Field distribution
in OPERA3D

14. Layout in experimental hall is almost fixed.
Layout in exp. hall
Layout in experimental hall is almost fixed.
Concept of yoke, shield is developed.
Detailed design of coil structure, cooling system, current leads etc. are underway.
~15 MPa
~30 MPa
SEQV
Model-2
FEM analysis of Mises stress in coils with thick outer shell
pure Al thermal link
GFRP(BT) spacer
GFRP(BT)
Al strip guide
lead cable guide
Welding to shell
Support Shell
2-phase He
CS0 coil structure
吉田君スライド。まだ設計段階で写真はないです。
Conceptual Design of
Tungsten Shield Supports
Supports 40ton shield
with <5mm distortion

15. Production Target Phase I (Radiation cooling)
Graphite (IG-43)
Refractory material and so is tolerant to high temperature operation
Experience in T2K
Tungsten (optional)
Larger muon yield
Radiation cooling may be OK but need careful assessment
Phase II (Active cooling)
Tungsten
Bad chemistry between tungsten and water
Helium cooling instead of water cooling
Chrisのノートから

16. Energy Deposit by 3. 2kW proton beam on a graphite rod (4cm diam
Energy Deposit by 3.2kW proton beam on a graphite rod (4cm diam. & 60cm L)
Chrisのノートから

17. Temperature distribution material emissivity of 0.75
Chrisのノートから

18. Accident Scenarios (Phase I)
Accidental fast extracted beam pulse
T2K target temperature rise in a cycle is 100K
sx = 4mm in T2k while sx=2mm in COMET
750 kW in T2K while 3.2kW in COMET
Well below graphite evaporation temperature
Detection system of extraction failure and temperature monitoring are mandatory
Loss of vacuum during operation
Any sublimation or oxidation ?
The COMET target is expected to run at a temperature well below the level
May be possible to contain the target within a thin metal capsule
Protects the target from oxidation and radiates the heat load
An alternative is
Coat the graphite with a refractory metal e.g. tantalum or iridium
Connecting the pump exhausts to a vessel through a filter system is an issue
Failure of any of dipole magnets bending the beam from the high-p line
Status will be included in MPS; If any of them is off, stop the accelerator
Even if any magnet fails during extraction, magnetic field goes down slowly due to the coil inductance and thus the beam won’t localize a small area on the beam duct/magnet.

19. COMET Phase I Facility Schedule
JFY
2013
2014
2015
2016
COMET building
design
construction
Solenoid magnet
SC wire
Capture magnet
Transport magnet
Cryogenic system
Magnet system test
Radiation shield
Beam dump
Pion target
Design & test
2013
Design of the building & beam line
Bid tendering and start construction
Design of superconducting solenoid magnets and start of construction
Production of SC wires as well
Design of the pion production target
2014
Completion of the building
Construction of superconducting solenoid magnets
Start magnet and radiation shielding (and beam dump) installation
Transport solenoid
Start preparation of cryogenic system
Tests of the target production target
2015
Preparation of cryogenic system
Construction of the pion production target
2016
Installation of the capture solenoid
Completion of the cryogenic system
Tests of the magnet system
Installation of the target
Ready to accept the 8GeV beam