Nov. 07 2004Beam Catcher in KOPIO (H. Morii) @ Mikata Kaon mini worksyop1 Beam Catcher in the KOPIO experiment Hideki Morii (Kyoto Univ.) for the KOPIO

Nov. 07 2004 Beam Catcher in KOPIO (H. Morii) @ Mikata Kaon mini worksyop 1

Beam Catcher in the KOPIO experiment

Hideki Morii (Kyoto Univ.)for the KOPIO collaborations

Contents1. What is Beam Catcher?2. Basic Design3. Expected Performance 4. Aerogel Quality Control System


Beam Catcher in the KOPIO experiment• KOPIO experiment measures KL 0mode• Identification : Detect and nothing veto

1. What is Beam Catcher?

Vetoing extra particle is predominant defense to BG


Beam Catcher

Catcher Module

Lead Converter


• Photon veto which covers beam core region

• under high neutron rate– ~10GHz (>10MeV)

• Need to be…– efficient to rays : 99% @ 300MeV– inefficient to neutrons : 0.3% @ 0.8GeV

• Aerogel Cherenkov + distributed geometry

– suppress neutron efficiency


Beam Catcher – MC Event DisplayEvent Display for Event Display for neutron

Top View Top View

Side View Side View

Secondary particles are created isotropically

Can distinguish from neutron using geometry

Shower spreads forward



Design of Beam Catcher – Single Module

• Lead converter– Size : 30 x 30 cm , 2mm thick

• Aerogel– Size : 30 x 30 cm , 5 cm thick– Refractive index : n ~ 1.05

• Mirror– flat mirror

• Funnel– Winston cone type

• PMT– 5 inch PMT

2. Basic Design


Top View

Design of Beam Catcher - Configuration

• Tapered configuration– 10 modules (front layer)

– 20 modules (back layer)

– 25 layers

• Number of modules– 370 modules

• Coincidence condition

2. Basic Design


Simulation – Efficiency for • Coincidence efficiency for

energy (GeV)

e

ffic

ienc

y

efficiency for

Y position (cm)

effi

cien

cy

3. Expected Performance

vertical position dependence

efficient region :±7cm

beam size


Simulation – Insensitivity to neutrons (1)

e

ffic

ienc

y

neutron kinetic energy (GeV)

coincidence efficiency for n

• Insensitivity to neutronsnumber of false veto

neutron yield

→2.8 % false veto prob.

coincidence count



Simulation – Insensitivity to neutrons (2)

• Single count rate by neutronssingle count rate by n

neutron spectrum

single count rate

→single rate ~ : 600kHz / module



Aerogel Quality Control System

(i) Transmittance– LED (light source) + PMT (photo detector)

(ii) Cherenkov light Yield– Solenoid Spectrometer (as source) + mirror + PMT

It is important to control optical properties of aerogel

4. Aerogel Quality Control System


Masked by black paper with a

2mmX2mm hole

UV,BLUE,GREEN,

YELLOW,RED

5-COLORS

•PMT with 2mm hole mask detects LED lightPMT with 2mm hole mask detects LED light•30mm x 30mm area is scanned at 2mm interval30mm x 30mm area is scanned at 2mm interval

by moving X-Y stageby moving X-Y stage

•position dependence of transmittance can be measuredposition dependence of transmittance can be measured

Setup for Transmittance Measurement

ApertureAperture ApertureAperturePMT on XY stage

Aerogel on X-Y stage

4. Aerogel Quality Control System : (i) transmittance


Transmittance -Rayleigh scattering-

λ(nm)(nm)

A=0.93

CT=0.0088m4

A=0.82

CT=0.0094m4

)exp(4CT

A Fit the function 1-A:Absorption CT:Rayleigh Scattering parameterA:Absorption CT:Rayleigh Scattering parameter

Absorption also increaseAbsorption also increase

The Tile with rough surface n=1.03

The tile with Clean surface n=1.03

tran

smitt

anc

e tran

smitt

anc

e

4

2cos1

dd

Note that Rayleigh scattering is dominant in Aerogel

Two parameters, A and CT, are used as the input to our MC simulation .

Can it predict correct light yield?

4. Aerogel Quality Control System : (i) transmittance


Measurement of Cherenkov Light Yield4. Aerogel Quality Control System : (ii) light yield

To measure Cherenkov light yield…

• Solenoid Magnet Spectrometer– source + gap type solenoid magnet

• Setup for light yield measurement– Spectrometer + mirror + PMT


Solenoid Magnet Spectrometersource＋ Gap-type Solenoid Magnet ==> Spectrometer

r

IRON

Electron rotate by Bz

COIL

GAP

Concept of Electron trajectory in this magnet

RuRu

0.8 m0.8 mMagnetic Field is strong near the gap

POINTTWO MAGNETS

•Large acceptance •High Resolution•parallel e- beam along Z-axis

We can get monochromatic electron beam

Variable Energy up to a few MeV

Beam intensity of ~30 Hz @2.5MeV

4. Aerogel Quality Control System :(ii) light yield


Spec of the Spectrometer

5.7

2670

7.5

2010 2400

13.7

820

10.1Resolution(%)

1460Energy（KeV）6． 310.1Resolution(%)

Energy（KeV）

Spectrum of Spectrum of focused electronfocused electron

［［ keVkeV ］］Energy spectrum of 106Ru

with and without magnet

［［ AA］］

Magnet Current VS peak e- energy

●●　　 datadata▲▲　　 ExpectationExpectation

［［ keVkeV ］］

4. Aerogel Quality Control System : (ii) light yield


from Spectrometer

Measurement of Cherenkov Yield by the Spectrometer

Cherenkov image on PMTCherenkov image on PMT

sourcesource

106Ru(3.541MeV)Ru(3.541MeV)

Setup

MCMC

5inchPMT5inchPMT

Two trigger Scintillators are placed downstream of 10f hole at the mirror surface



Cherenkov Yield Energy Dependence Measurement1

▲▲　ＧＥＡＮＴ　ＧＥＡＮＴ●●　ＤＡＴＡ　ＤＡＴＡ


n=n=１．０１．０３３

TR=67TR=67％％@470nm@470nm

n=n=１．０１．０5 5

TR=69TR=69％％@470nm@470nm

We measure the Cherenkov light yield We measure the Cherenkov light yield with changing the energy of electronwith changing the energy of electron

Incident Energy of electronIncident Energy of electron Incident Energy of electronIncident Energy of electron

P.EP.E P.EP.E

Example of the results for two aerogel samples (thickness=11mm)Example of the results for two aerogel samples (thickness=11mm)

with similar transmittance but different refractive indexwith similar transmittance but different refractive index



Summary• Beam Catcher

– Photon detector positioned in neutral beam Need to have enough g efficiency Need to insensitive to neutrons

• Design– Pb + Aerogel Cherenkov counter with distributed geometry

• Expected Performance– 99% @ 300MeV / 0.3% @ 800MeV ~3% false veto prob.

• Aerogel quality control system– Transmittance– Cherenkov light yield

Summary


Extras


Beam Catcher – Prototype Test• Light yield – using +

• Neutron inefficiency

- using proton in place of neutrons

Prototype Module

Light Yield Proton Efficiency

Data matches MC very well


Simulation – Insensitivity to KL (1)

Coincidence efficiency for KL False veto probability by KL

→ ~2.3% false veto prob.


Simulation – Insensitivity to KL (2)

→ single rate : ~330 kHz

Single count rate by KL


Cherenkov Yield Energy Dependence Measurement2

n=1.03n=1.03TR=67%@470nmTR=67%@470nm


n=1.03n=1.03TR=85TR=85％％@470nm@470nm


1.5 P.E1.5 [email protected]@2.4MeV

A=0.82

CT=0.0094μm4

A=0.94

CT=0.0044μm4

1.9 P.E1.9 [email protected]@2.4MeV

Incident Energy of electronIncident Energy of electronIncident Energy of electronIncident Energy of electron

P.EP.E P.EP.E

Example of the results for two aerogel samples (thickness=11mm)Example of the results for two aerogel samples (thickness=11mm)

with the same refractive index but different transmittancewith the same refractive index but different transmittance

4. Aerogel Quality Control System

Documents

Nov. 07 2004Beam Catcher in KOPIO (H. Morii) @ Mikata Kaon mini worksyop1 Beam Catcher in the KOPIO experiment Hideki Morii (Kyoto Univ.) for the KOPIO