CLAS12 activity at IPNO D2I:

Design, realization and test of the Central Neutron Detector

J. Bettane, J.L. Cercus, B. Genolini, G. Hull, M. Imre, A. Maroni, T. Nguyen Trung, J. Peyré, J.

Pouthas

Introduction: the CND for CLAS12

Design of the detector

Test on the prototypes

Detector status

Summary - Outline

Pag. 1

Introduction: from CLAS to CLAS12

Pag. 2

ContinuousElectronBeam

AcceleratorFacility

Hall BHall A Hall C

Emax = 6 GeV

Emax = 12 GeV

Jefferson LaboratoryNewport News, USA

CLAS12: Study of the proton and neutron structure via the deeply virtual Compton scattering

Introduction: The Issue

Pag. 3

Limited space available

Strong magnetic field (~5T)

Scintillator barrel and long light

guide

Neutron Detector to be added in the CLAS12 CD

Introduction: The proposed solution

Pag. 4

Really challenging to collect the light on one side of the

scintillatorUse a “U turn” light guide to collect the light at the

same side

24 elements of 6 scintillators each:

144 scintillator bars and 144 PMTs

Definition of the prototype

Pag. 5

TEST !!! ?

Shield PMT Wrap Scintillator

Glue U-turn

- 2.5 mm - R2083 - Mylar Al

- BC408 - M-BOND 200

- Triangular

- 5 mm - 9954A - VM2000

- EJ200 - BC 600 - Semicircular

- R9779 - Al foil

- R10533

Light yield and time resolution study

Pag. 6

PMT Ind

PMT DirCosmic ray

γ γ

We need to know the interaction point

PMT

PMT Bottom

PMT Top

POS

-2 -1 0 1 2

-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.50.0

50.0

100.0

150.0

200.0

250.0

300.0

Position

Tim

e R

esolu

tion

[p

s]

Dir

Ind

TRG

Pag. 7

Magnetic field test @ LAL

Average magnitude of the magnetic field at

the location of the PMTs of the CND: B ~

215 G

0 0.5 1 1.5 2 2.5 30

50

100

150

200

250

300

350

400

450

Amp400 θ=0 MS=2.5

Amp400 θ=0 MS=5

I [A]

Sig

nal

Am

pli

tud

e

[mV

]

x2

Pag. 8

Test on the prototype

Definition of the prototype

Pag. 9

Shield PMT Wrap Scintillator

Glue U-turn

- 2.5 mm - R2083 - Mylar Al

- BC408 - M-BOND 200

- Triangular

- 5 mm - 9954A - VM2000

- EJ200 - BC 600 - Semicircular

- R9779 - Al foil

- R10533

Better σtSame LY and σt, cheaper

Better σt (worst LY), cheaper

Good σt, cheaper

“Play safe”

- Optical grease- Silicone cookie- Optical glue

Better mechanica

l properties

Electronic read-out 1

Pag. 10

High gain PMT to avoid the need of preamps

Active splitter from G0

Charge measurements: flash ADCs (provided by JLab) CAEN V1720 @ 250 MHz

Time measurements: 100 ps/ch TDCs (provided by JLab)

Test @ position 0. TDC with 50 ps/ch, 75 ps/ch and 140 ps/ch provided same results

PMTHV

SplitterCFD

ADC

TDC

Electronic read-out 2

Pag. 11

Time measurements: CFD Best results with ENERTEC CFD G0 type

Too much R&D and design needed – no pursued further

16 channels CAEN N843Maybe usable after modification by CAEN – no pursued further

4 channels ORTEC 935 (ENERTEC equivalent) Too low density and too expensive

16 channels GAN ELEC FCC8 Results as good as with ENERTEC CFDLong term loan from Germany

Status of the detector construction

Pag. 12

150 PMTs purchased from Hamamatsu. Calibration tests on-going

20 PMTs HV divider ready and other 130 on-going

All the scintillator purchased and delivered

μ–metal purchased and delivered (150 tubes Ø60x215 mm3)

Mild steel to be ordered

The light guide design will be finalized before spring 2013 and then the order will be place before summer

Pag. 13

Summary and future work

Final design established – and different element chosen

Scintillator EJ200 + PMT R10533 + 1500 mm long light guide + Al foil wrapping + 1 mm thick μ-metal and 5 mm thick mild steel shielding + semicircular light guide at the

“U turn”σt(Dir) ~ 120 ps σt(Ind) ~ 210 ps The detector assembly will start in the fall

2013 Each block of 6 scintillators will be assembled and tested separately prior expedition to US Expedition to US during summer 2014

The END!!!!