Development of an Aerogel-based Photon Detector - PowerPoint PPT Presentation

1 / 26
About This Presentation
Title:

Development of an Aerogel-based Photon Detector

Description:

Light collection with. Flat mirror & Winston cone. Sparse 'sandwich' detector. modules' array ... 30GeV proton, 100 TP/spill. Small production angle, relatively ... – PowerPoint PPT presentation

Number of Views:30
Avg rating:3.0/5.0
Slides: 27
Provided by: tno8
Category:

less

Transcript and Presenter's Notes

Title: Development of an Aerogel-based Photon Detector


1
Development of an Aerogel-based Photon Detector
  • T. Nomura (Kyoto Univ.)

2
Motivation, Challenge, and Solution
A part of veto detector in rare KL experiment
Located in intense neutral beam
Aerogel-based photon detector
3
Motivation
  • Necessary in KLgp0nn measurement
  • Importance of KLgp0nn
  • CP violating process
  • Branching ratio proportional to Im(Vtd)2,
    BR10-11
  • Very small theoretical uncertainty (1)
  • Play an important role to explore BSM (like SUSY)
  • Difficulty of KLgp0nn experiment
  • All neutrals in initial and final states
  • Event signature 2g (from p0) nothing (2n)
  • We have to prove nothing in order to suppress
    backgrounds
  • KL?p0 p0p0 (BR 21), p0 pp- (BR 13), p0 p0 (BR
    10-3),

4
Motivation
To prove nothing, we needs Hermetic veto
system
Need to catch photons escaping through
the beam-hole
What we want to develop !!
5
Challenge
  • In-beam environment
  • High intensity neutral beam (necessary to
    observe gt100 KL?pnn events in 2-3 years)
  • A vast amount of neutrons (a few10GHz)
  • Produce protons, pions, (g and e/e-) in the
    detector
  • Most KLs survive after decay region (100MHz)
  • Decay into p, g ,e/e- in the detector
  • ? These secondary particles fire the counter
    and disturb its primary function !!

6
Solution
  • Utilize Cherenkov radiation Aerogel (low
    refractive index 1.05) radiator
  • Avoid detection of slow particles from neutron
    interactions Slow p, p and other hadrons cannot
    emit lights.
  • Use direction information Segment the detector
    into many modules and require coincidence
    along the beam direction
  • Catch forward photons only Reduce fake signal
    due to g from secondary p0 (neutron interaction
    and KL decay in the detector)

7
Design of In-Beam Photon Detector
  • Module
  • Pb (g converter) Aerogel (Cherenkov
    radiator)
  • Light collection with Flat mirror Winston
    cone
  • Sparse sandwich detector
  • modules array

8
Proof of Principle (I)
  • Weve made three generations of prototypes
  • Prototype 1 (2001-2)
  • Simple structure
  • 11cm x 11cm tiles
  • Flat mirror
  • Read by 5-inch PMT
  • Exercise to use aerogel detector
  • light yield

9
Proof of Principle (II)
  • Prototype 2 (2002-3)
  • Sophisticated optics
  • 11cm x 11cm tiles
  • 2-axis parabolic mirror
  • Read by 5-inch PMT
  • light yield
  • response to proton (as substitute for neutron)

10
What we learned from Prototype 2
  • Response to Proton(analogous to neutrons)
  • Single module efficiency
  • Find N2 gas scintillation(problematic in 1p.e.
    region)
  • Two layers coincidence
  • Good agreement with MC

11
Proof of Principle (III)
  • Prototype 3 (2004-5)
  • Base design
  • 30cm x 30cm area(3x3 of 10cm sq. aerogel tiles)
  • Flat mirror
  • Winston cone
  • Read by 5-inch PMT
  • light yield
  • position / angular dependence

12
Elements of Prototype 3
  • Elements
  • 3x3 10cm sq tiles, stacked 5 layers
  • Winston cone
  • made by thin Al
  • AlSiO2 evaporated on inner surface

45 Tiles made by Matsushita
Made by Yokohama-Kiko
13
What we learned from Prototype 3 (i)
  • Position dependence
  • Global structure, reproduced well by MC
  • Edge effect between tiles
  • surface deterioration by trimming process
    (water jet)

By Winston cone entrance (x6cm)
By tiles edge effect (x5cm)
14
What we learned from Prototype 3 (ii)
  • Angular dependence
  • Global structure, reproduced well by MC
  • Winston cone deformed
  • stressed by joint or support

By cones acceptance (q7 deg)
Reflection anglemeasured by laser
By cone deformation (q5 deg)
15
Practice in KEK E391a experiment
  • E391a-III had run
  • with this Prototype 3
  • called APC (Aerogel Photon Catcher)
  • Used as in-beam g tagger

BA (Beam Anti) E391a in-beam detector PWO
Quartz sandwich
16
Application
To KOPIO experiment at BNL
To KLgp0nn experiment at JPARC
17
KOPIO experiment
Terminated (2005 August)
  • Planned KLgp0nn experiment at BNL
  • (Construction 2006-, Run 2010-)
  • High intensity proton beam
  • 100 TP/spill
  • Soft KL beam
  • 0.5-1.0 GeV/c
  • Horizontally wide beam
  • 4mrad x 90mrad
  • Measure g direction as well as energy
  • Sensitivity 40 SM events (S/N2), or 200 SM
    events (S/N0.3)

18
KOPIO detector Beam Catcher
19
KOPIO In-beam Photon Detector
  • In-beam Aerogel Detector
  • Module size 30cm x 30cm
  • Module array
  • Number of modules 420
  • 12-21 in horizontal with beam divergence
  • 25 layers along beam(8.3 X0 in total)
  • Z gap between layers 35cm

20
Expected Performance by MC (1)
In KOPIO case
  • Photon efficiency
  • Soft KL in KOPIO
  • Relatively low energy g
  • Relatively small shower
  • Low threshold

Coincidence condition 4 p.e in A, 2 p.e. in B
21
Expected Performance by MC (2)
In KOPIO case
Hit probability for Neutrons
Hit probability for KLs
Dominated by decays in the detector
0.3 _at_ 800MeV
22
Application to Experiment at J-Parc
  • KLgp0nn experiment plan at J-Parc
  • 30GeV proton, 100 TP/spill
  • Small production angle, relatively hard KL beam
  • Pencil beam
  • ( a few 10 ) mstr, 10cmf at the detector
  • Step 1 with (modified) KEK E391a detector
  • 10 SM events, Discovery phase
  • Step 2 with new, optimized detector
  • Precision measurement, 100 SM events

23
In-beam Detector for J-Parc experiment
  • In contrast with KOPIO case
  • Pencil beam
  • A series of modules along beam direction
  • Relatively high energy g (neutrons)
  • Detection threshold can be (has to be) higher
  • 3 consecutive hits, 424 p.e.

24
Expected Performance
In J-Parc case
  • Neutron Hit probability
  • Level of 0.1 _at_ 4.0GeV/c
  • Photon efficiency
  • 90 efficiency _at_1GeV
  • 99 efficiency _at_2GeV
  • At high energy limit, inefficiency O(10-3)

25
Expected Performance
In J-Parc case
With various threshold
26
Summary
  • Weve developed Aerogel-based Photon
    Detector to use in intense neutral beam
  • One of the key detectors in KLgp0nn experiment
    to explore physics beyond the SM
  • New concept
  • Pb (converter) Aerogel (Cherenkov radiator)
  • Sparse sandwich detector
  • Proof-of-Principle done with 3 generations of
    prototypes
  • Originally, it was designed for KOPIO
    experiment.Now, we are considering to use this
    detector at J-PARC

27
Signal Loss due to False Hit
In KOPIO case
  • Accidental hit due to neutrons may kill K?pnn
    signal
  • Total false hit probability was found 0.4
    events / m-bunch
  • Integrated over the duration consistent with
    the arrival time of g from our signal KL
  • If we set the time window to be 3ns,signal loss
    due to false hit will be 4.6
  • Calculation based on random effect
  • Detailed studies by MC under way

Apply timing cut
28
False Hit Rate due to neutron (Step1)
In J-Parc case
  • Accidental hit due to neutrons (In case
    Step 1)
  • Integrate over neutron momentum
  • Enough low rate (1MHz) even with lowest thres.

29
False Hit Rate due to neutron (Step2)
In J-Parc case
  • Accidental hit due to neutrons (In case
    Step 2)
  • Very high rate (10MHz) even with highest
    thres.

30
Signal / Background (Step2)
In J-Parc case
  • To gain background rejection power
  • Prefer lower threshold
  • To prevent acceptance loss due to false
    veto
  • Prefer high threshold
Write a Comment
User Comments (0)
About PowerShow.com