Design of JPARC Neutrino Beamline and R

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Design of J-PARC Neutrino Beamline and RD of
Beam Monitors
K. Tanabe
Outline
Simulation study of the J-PARC primary proton
beamline
Estimation of beam loss and design parameters
Collimators, Radiation shield
RD of proton beam profile monitor
Segmented Secondary Emission Monitor (SSEM)
Beam test at the KEK-PS Neutrino Beamline
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Simulation study of the J-PARC primary proton
beamline
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Introduction - J-PARC neutrino beamline -
J-PARC??????????? K2K??100?
(750 kW)
???????????????????????
(Total Beam loss limit 1W/m in Arc)
??????????????????
????????????
(Point loss limit 10W/1magnet)
50GeV ring
Preparation section
50m
Conventional magnet
Arc section
Beamline????????????????????????????????
150m
Super-conducting magnet
Final Focusing section
40m
Conventional magnet
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Collimators and Shield in Preparation Section
Beam core e 6 pmmmrad
, dP/P 0.3
Acceptance
Preparation section e 60 pmmmrad
Arc section larger than preparation section
To control the energy deposit in the arc section,
the design of the preparation section is
important.
We have varied the design parameters, and
estimated the beam loss in the arc section.
Components we studied with simulation
Preparation section
Beam
Collimators
Radiation shield at the exit of the preparation
section
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Simulation Setup with Geant4
Preparation section
Beam halo parameter
Arc
Ebeam 50 GeV
dP/P 2.0
e 0200 pmmmrad (uniform distribution
in phase space)
energy deposit MeV
proton hit number
Final Focus
Inject beam halo, estimate beam loss in the arc
section.
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Simulated beam loss at each component
Total beam loss
2.7W
? 750W
energy deposit MeV
proton hit number
Total beam loss in preparation section is assumed
750W (0.1).
On this assumption, energy deposit in each
component are normalized.
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Collimator design
To protect the Arc magnets from beam loss,
collimators in preparation section scrape off
the beam halo.
Current design
Thickness 50 cm
Fills up as much drift space as possible.
Length 1.45 3.0 m
Gap height 3.1 9.5 cm
These gap sizes are designed to accept particles
in e 60 p mm mrad .
Gap width 6.4 12.1 cm
? Very large collimators (very conservative)
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Collimator design - Thickness of collimators -
We checked whether we can make collimators
smaller
without increase of the beam loss in
super-conducting magnets in arc section and
conventional magnets in preparation section.
Magnets around the collimators at the preparation
section
Calculation result indicates that
5cm is thick enough.
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Collimator design - Length -
We changed the length of collimators
Baseline design (4 collimators fill up as much
drift space as possible)
? 50cm, 10cm.
Total energy deposit in Arc section
Making collimators shorter increases energy
deposit in the arc section.
Length of the collimators must be long.
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Radiation Shield at the exit of preparation
section
Tunnel wall
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
showers
Beamline
Assumed shield size
1m thick, 3m wide (tunnel filler like illustrated
in the left figure)
3 m
Preparation section
Arc
material of shield
concrete, iron or tungsten
1 m
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Radiation Shield at the exit of preparation
section
The inner diameter of the shield
result is nearly identical with those without
shield.
100mm
smaller (50 or 60mm)
the energy deposit in the arc section increased
due to the shower particles generated at the
shield.
Without Shield
Concrete
Fe
W
The current simulation result does not support
the idea of having the radiation shield at the
exit of preparation section.
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Summary - simulation study
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.
Collimator
Thickness 5cm is good enough.
length gt 1m needed.
Radiation shield at the exit of preparation
section
The current simulation study does not support.
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Primary Proton Beam Profile Monitors
-Segmented Secondary Emission Monitor-
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Introduction
Desired Performance of profile monitors at the
J-PARC Neutrino beamline
High intensity proton beam induces large
radiation dose.
Low material, long lifetime, easy maintenance
(In case of SSEM, movable structure will be
required.)
Wide dynamic range to operate from the initial
low beam intensity to full design intensity.
(1012 1014 protons/pulse)
Profile measurement resolusion required about
12mm.
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Principle of SSEM
SEM (Secondary Emission Monitor)
Thin metal foils are inserted across the beam.
If the beam transverses the foils, secondary
electrons are emitted from cathode electrodes,
and are absorbed by anode electrodes.
Segmentation of cathode electrodes with
wire/strips,
enables to measure the beam profile.
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SSEM - Beam test Purpose -
Requirement for SEM cathode materials
High efficiency of the secondary electron
emission
Low amount of materials interrupting the beam
Resistant to heat and sputtering
Etc
We carried out two beam tests at the K2K neutrino
beamline.
1st beam test
Check the basic response of SSEM with K2K proton
beam (6x1012 protons/pulse)
Compare the difference of signal intensity among
5 cathode materials.
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SSEM - Beam test Setup -
10X10cm
1.5cm
Placed alternatively at intervals of 7mm.
Al
Cathode
Anode
Beam size vertical size 4cm
horizontal size 2cm
Width of strip 1.5cm.
? require several nC/channel.
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SSEM - Beam test Setup -
Vacuum Chamber
10-6 Torr
150m?Twisted pair cable
Oscilloscope
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SSEM - Beam test Basic responses -
anode voltage dependence of the signal height
Beam Intensity 4.3e12 ppp
Fig Cu ch2(center) pulse height
Hereafter, we set the anode voltage to be 200V.
Confirm one basic response Signal
height was saturated around 100V.
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SSEM - Beam test Basic responses -
Measured signal wave form (oscilloscope)
Vacuum 10-6 Torr
Anode voltage 200V
9 peak structure can be seen. (K2K beam
9bunch/1pulse)
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SSEM - difference in cathode materials -
Secondary emission efficiencies for the different
cathode materials.
All measured secondary emission efficiencies are
in the same order.
result of the 70MeV electron beam experiment at
SLAC.
NIM 39 (1966)p.303
Tungsten is 4 times larger than aluminum in
interaction length.
Light materials, like Al ,Ti, are preferable.
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SSEM - test of the fine segmented cathode -
Cathode????ch???K2K?DAQ(Charge???ADC)?????????????
????????
Pulse Trans
Attenuator (20dB)
Ti strip(2mm?)
ADC
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SSEM - test of fine segmented cathode -
??????????????
SSEM
????????
???????
SSEM??1m?????SPIC
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Summary - SSEM
We have started the RD of SSEM as a beam profile
monitor for the J-PARC neutrino beamline.
In these two beam tests at the K2K neutrino
beamline,
We confirmed the basic responses of SSEM.
Secondary emission efficiencies are in the same
order in 5 cathode materials.
? In terms of interaction length, Al or Ti is
preferable.
We test the fine segmented cathode electrodes,
with Ti strip(2mm).
?We demonstrate the beam profile measurement with
SSEM.