SLIDE 1
Simulation study of the J-PARC primary proton beamline
Outline Introduction Simulation setup Collimators Summary Radiation shield Estimation of beam loss and design parameters
SLIDE 2 F Q 4 F Q 3 B F Q 3 A F H 2 F V FQ2B FQ2A F H 1 F Q 1 P Q 4 B P H 3 P V 2 P Q 5 P V 1 P Q 3 B P Q 4 A
1.92 deg. bend
PQ2B P D 2 P Q 3 A PD1 PQ1
1.92 deg. bend
PQ2A
ニ ュ ート リ ノ ・ ビ ーム ラ イ ン
PH1 PH2
Introduction - J-PARC Neutrino beamline -
Final Focusing section Arc section 50GeV ring ~40m
Super-conducting magnet
Conventional magnet
(Total Beam loss limit : 1W/m in Arc)
Conventional magnet
(Line loss limit : 10W/1magnet)
The Arc Section consists of super-conducting magnets. Proton Beam Power at J-PARC ~100 times larger than K2K
Preparation section ~50m
It is very important to reduce the beam loss in the arc section in designing the proton beam line.
~150m
Beam loss induces large radiation dose. Protect the super-conducting magnets from quenching (750 kW)
SLIDE 3
Collimators Radiation shield at the exit of the preparation section Acceptance Preparation section : ε =60 [π∗mm*mrad] Beam core: ε =6 [π∗mm*mrad] , dP/P = 0.3%
Collimators and Shield in Preparation Section
Arc section : larger than preparation section Components we studied with simulation Preparation section We have varied the design parameters, and estimated the beam loss in the arc section. Beam To controll the energy deposit in the arc section, the design of the preparation section is important.
SLIDE 4 Final Focus Arc Preparation section
Simulation Setup with Geant4
ε = 0~200 [π∗mm*mrad] (uniform distribution in phase space) dP/P = 2.0%
p r
h i t [ n u m b e r ] e n e r g y d e p
i t [ M e V ]
x x’ Inject beam halo, estimate beam loss in the arc section. Beam halo parameter Ebeam = 50 GeV
SLIDE 5 Simulated beam loss at each component
p r
h i t [ n u m b e r ] e n e r g y d e p
i t [ M e V ]
Total beam loss in preparation section is assumed 750W (0.1%). Arc FF Total beam loss 750W 3.7W On this assumption, energy deposit in each component were normalized. Preparation section 508W Total loss deposited in components
energy deposit [MeV] 150 200 250 100 50 1 103 106 109
SLIDE 6 To protect the Arc magnets from beam loss, collimators in preparation section scrape off the beam halo. Thickness : 50 cm Current design
length gap width gap thickness beam beam
Collimator design
Length : 1.45 ~ 3.0 m Gap height : 3.1 ~ 9.5 cm Gap width : 6.4 ~ 12.1 cm Very large collimators (very conservative) These gap sizes are designed to accept particles in ε = 60 [π * mm * mrad] . Fills up as much drift space as possible.
SLIDE 7 10 20 30 40 50 60 2 3 4 Energy Deposit [W] Collimator Thickness [cm] Fe W Arc Total
Collimator design - Thickness of collimators -
10 20 30 40 50 60 10 20 Energy Deposit [W] Collimator Thickness [cm] Fe Collimator PQ3 PV2 PQ4 PH3 PQ5
Magnets around the collimators at the preparation section
without increase of the beam loss in super-conducting magnets in arc section and conventional magnets in preparation section. We checked whether we can make collimators smaller Calculation result indicates that 5cm is thick enough.
SLIDE 8
1 2 3 4 5 6 Energy Deposit [W] nominal 50cm 10cm Collimator Length
We changed the length of collimators.
Collimator design - Length -
Making collimators shorter increases energy deposit in the arc section. Arc Total Length of the collimators must be long.
SLIDE 9
Assumed shield size :
Radiation Shield at the exit of preparation section
In order to protect the super- conducting magnets from shower particles generated in preparation section, radiation shield can be placed at the exit of the preparation section. Shield Tunnel wall Beamline Preparation section Arc showers ~3 m 1 m material of shield : 1m thick, 3m wide (tunnel filler like illustrated in the left figure) concrete, iron or tungsten
SLIDE 10
40 60 80 100 120 5 10 15 Energy deposit [W] Shield gap size [mm] Arc Total 40 60 80 100 120 5 10 15 Shield gap size [mm] @ Arc 1st CF magnet
The current simulation result does not favor the radiation shield at the exit of preparation section. the energy deposit in the arc section increased, due to the shower particles generated at the shield. Without Shield The inner diameter of the shield :
Radiation Shield at the exit of preparation section
Concrete Fe W result is nearly identical with those without shield. 100mm smaller (50 or 60mm)
SLIDE 11
Thickness : 5cm is good enough.
Summary
We have carried out the J-PARC proton beamline simulation studies. We estimated the beam loss, and studied the design for collimators and radiation shield. The current simulation study does not favor. Collimator length : > 1m needed. Radiation shield at the exit of preparation section
