FoCal Project in ALICE

Yota Kawamura for the ALICE FoCal collaboration
TCHoU workshop
2018/3/15

1Outline✦ Introduction of FoCal Project✦ Motivation✦ Detector design✦ The result of past test beam(2014~2016)✦ Activity in 2017
✦ Production of new Si detector✦ Test beam at ELPH
✦ Summary

TCHoU workshop 2

FoCal project
ALICE detector

LHC✦FoCal：Forward Calorimeter‥ Electromagnetic calorimeter installedin the forward direction (3.3 <η <5.3)✦ALICE upgrade planー＞Install finished machine in 2024 (LS3)✦Experimental verificationof CGC by direct photon measurement8m
FoCal in ALICE detector
TCHoU workshop 3

Motivation

The time scale of collision

What is the nucleon
before the collision ?
Low energy

High energy
GluonQuark

Bjorken-x
Parton distribution
as a function of Bjorken-x
at Q2 = 10 GeV22pT yx= p esSmall-xx  10 4‥CGC occures？

Nuclear form before nuclear collision ‥✦ Model ”Color Glass Condensate(CGC)” ‥the saturation of gluon✦ Access to information in the initial stage of collision‥Low x , that is at high energy and forward region

TCHoU workshop 4

Direct Photon measurement
NLO pQCD

Experimental validation Probe ‥Direct (isolated) photon

CGC model
Direct photon R_pA
η = 4, p+Pb,√s = 8.8 TeV

1515Direct γ

101010555000−5−−55−10500GeV direct photons−15longitudinal depth : 5X
−15−10−50510015X (mm.)π0 →γγ4mm

Y (mm.)

151, high position resolution enough to separation γ/π02, energy measurement with wider dynamic range
YY (mm.)(mm.)

Y (mm.)

Requiredperformance

1, HGL(high Granularity Layer)‥High position resolution (MAPS detector)
2, LGL(Low Granularity Layer)‥Energy measurement (PAD detector)
151050−5−−1010500GeV500GeVdirect
π0 decayphotons
photons−−1515longitudinallongitudinaldepth
depth::10X5X00−−1515 −−1010−−5500

5510101515XX(mm.)(mm.)−10500GeV π0 decay photons−15longitudinal depth : 10X−15−10−50510015X (mm.)

simulation by GEANT4
TCHoU workshop 5

FoCal design

LGL

HGL

University of Tsukuba

Utrecht Univ.

Si/W sandwich constructer
W: Absorber
1X0 = 3.5 mm(1layer)
RM = 9.3 mm2 types of Si sensor
1. LGL(Low Granularity Layer)
Si Pad1Pad = 1 ⇥ 1 cm21layer = 64 Pads(8 ⇥ 8)
Energy measurement
2. HGL(High Granularity Layer)
Monolithic Active Pixel Sensors(MAPS)
1pixel = 30 ⇥ 30 µm2
digital readout
High position resolution

LGL

HGL

Straw man design
TCHoU workshop 6

counts/Nevts

Performance evaluation of the prototype
counts/Nevts

Energy Distribution

0.06

0.12

beam

0.05

10 GeV
20 GeV
30 GeV40 GeV
50 GeV

0.1

0.08

0.03
0.02

0.04

0.02

0.01

0Energy Resolution [%]LGL204060×1080
100ADC sum (ch)3ADC distribution

HGL110 GeV

0.040.06

LGL130 GeV

00246×106
8 10 12 14 16 18 20
ADC sum (ch)30
test beam 2016
22y= (9.7) +(25.7)E22y= (5.1) +(12.8)
ideal simulation
E2 10.7 2simulation(with dead ch) y= (10.1) +( E )25test beam 2015

20
15

✓Take data up to 130GeV✓Energy resolution 15%

10500

Test beam at CERN SPS in 2016

2040

60

80

100 120 140

Beam Energy [GeV]✦ Test beam ORNL (Oak Ridge National Laboratory)
prototype until 2014〜2016
next‥ MIP measurement and more wider dynamic range
Improve energy resolution

7

Activity in 2017
✦ Trial in this year‥

Production new prototype(The first attempt of Japan FoCal group)

Ongoing✦Evaluation of basic characteristics✦Si-Pad Design optimization✦Si detector production✦Test beam (at Tohoku univ. ELPH )MIP ~ Low Energy measurement

Si-Pad detector
1ch monitor PD forbasic characteristics test

Si detector (8×8 ch)

8Production
Double-sided
adhesive tapeFlexible printed circuits
Si PAD made by Hamamatsu
1cm2 Pad size 8×8 cellPicture when boning

Bonding machine

Comple !

Bias circuit and read line to each cell,
GND connect with siliconwith wire of several 10 µm thickness

9

Readout System
APV25(CERN RD51)

SRS(Scalable Readout System)(CERN RD51)

readout chippreamp, shaper
128 ch : output
Sampling frequency:40MHz
5Gains: 80,90,100,110,120%

ADC Board:12bit 16ch ADC
128 16 = 2048ch
FEC Board: front-end
Control of digital information
by FPGA on FEC
UDP communication by GbE

HDMI

Detector

GbESRS• AD conversion• Front end

mmDAQ(PC)• Online monitor• Data taking

TCHoU workshop 10

Set up
JIG, Electric Stage
Detectorbeam①②: 10×10 cm③: 4×4 mm①W platedetector②③W plate (3X0)
Trigger scintillator✦Date: December 15 - 22 at ELPH in Tohoku University✦800 MeV/c e+ beam
✦Generate beam trigger with coincidence of three scintillator✦Place 3X0 tungsten plates in front of the detector to raise a shower(take data with W on and off)
TCHoU workshop 11

Result MIP response
1 MIP

160
140120
100

2 MIP

8060

3 MIP?

40count 2000200

400

600

ADC (ch)

800

1000

1200

1400

1600

1800

2000

deposit Energy (MeV)

GEANT4 simulation✦ 1 Pad ADC distribution✦1 Events that two electrons, three entered in Pad, can also be observed(peak is proportional to number of electron)✦Consistent with GEANT412

MIP ADC (ch)Characteristics of each channel

ADC (ch)

500
450

8400

7350

6300

5220

210

200

250

190

4200

3180

150
2100

170

50

10000

1020304050

6070chMIP ADC channel as a function of ch

123

4

5

68×8 hit map✦Without tungsten : beam behave as MIP✦Variation < 10 %(Pad and electronics characteristics ? )✦Signal is smaller at the edge-> Because of dark current ?
or signal attenuation due to wiring length ?

78160

13

Efficiency• Efficiency = hits / entries
hit ‥ Number detected by padentries ‥ Number detected by the trigger

number of hits

✦Total efficiency is about 97%‥The beam is not narrowed down to 1 channel
TCHoU workshop 14

Summary✦ FoCal project‥Electromagnetic calorimeter scheduled to beinstalled in front of ALICE detector✦Silicon Detector production for the first time
✦ELPH test・ Successful observation of MIP signal・ the variation of PAD < 10 %・ efficiency 97 %Next‥
✦Production of prototype for real machine by increasing thelayer of silicon as a calorimeter✦Dynamic range expansion to enable observation of highparticle energy in the forward direction

TCHoU workshop 15

Thank you very much for your attention !

16

back up

データ構造✦APVのサンプリング周波数40MHz（25nsec）ごとにAPV128 ch分の波高をADCにして読み出す

TCHoU workshop 18

MIP
χ2 / ndf
ProbConstant
MPVSigma

120

100

204.7 / 1860.1653
601.2 ± 18.0
195.3 ± 1.0
23.69 ± 0.57

80604020002004006008001000

1200

140016001800

2000

1MIPの分布（Wを置かない場合のデータ）
TCHoU workshop 19

Linearity
Energy Dependence

3×1010000

ADC sum value [ch]ADC_SUM [ch]

80000

70000

60000

50000

9000

ADC [ch]=5.57×104E [GeV]+3.52×103 [ch]

8000
7000
6000
5000

40000

4000

30000

3000

20000

2000
10000

01020304050
Energy [GeV/c]

0020406080

100 120 140

Beam Energy [GeV]

Ratio

01000

1.08
1.06
1.04
1.02
10.98
0.96
0.94
0.92 01020304050

Energy [GeV/c]

TCHoU workshop 20

ADC_SUM [ch](data)×103130 GeV

3500

700

110 GeV

3000

600

2500

500

2000

400

1500

300

1000

200500100002460
8 10 12 14 16 18 20
Radiation length [X ]deposit energy [MeV](simulation)

Longitudinal shower growthbeam test result
simulation (with dead ch)ideal simulation

0LGL1LGL2 LGL3 LGL421