Detector%R&D%of%the%Forward%Calorimeter%with%PAD%
readout%for%the%ALICE%upgrade

Masahiro!Hirano,!Tatsuya!Chujo,!Motoi!Inaba!University!Of!Tsukuba!for!the!ALICE!FoCal!collabora'on

University*Of*Tsukuba

FoCal%projectFoCalOE%strawman%design
FoCal2E!is!an!electromagne'c!calorimeter!
consis'ng!of!the!tungsten!and!silicon!
sensors!with!a!sandwich!structure(Fig.2).!

IntroducLon!
FoCal(Forward!Calorimeter)!is!a!project!under!study!within!the!ALICE!Collabora'on!for!a!possible!
upgrade!during!the!LHC!Long!Shutdown!3(2024).!
FoCal!has!two!components!:!FoCal2E!and!FoCal2H!and!would!be!installed!7m!from!collision!point!as!
shown!in!Fig.1.!
The!main!goal!of!FoCal!is!the!iden'ﬁca'on!of!direct!photons!and!decay!photons!in!pp,!p2Pb!and!Pb2Pb!
collision.!

FoCal2E!have!2!diﬀerent!module!
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!2!Low!Granularity!Layer(LGL)!
!!!!!!!!!!!!!!!!!!!!!(Fig.3←This!is!our!R&D!prototype!!)!
!!!!!!!1!segment!=!4!layers!of!Si/W!
!!!!!!!1!layer!has!64!PADs(8!×!8)!
!!!!!!!PAD!cell!size!:!1!×!1!cm2!
!!!!!!!signals!are!longitudinally!summed!
!2!High!Granularity!Layer(HGL)!
!!!!!!!!CMOS2pixel!
!!!!!!!!pixel!size!:!25!×!25!μm2!
!!!!!!!!Digital!signal!are!summed!in!1!mm2!cells

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W/Si!sandwich!calorimeter!
!2!W!absorber!+!Si!sensors!
!!!!!!!Moliere!radius!!!!!:!RM!=!9.3mm!
!!!!!!!Radia'on!length!:!X0!=!3.5mm!

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MoLvaLon%!2!to!study!the!ini'al!state!of!nuclear!collisions!at!high!energy.!
!2!measurement!of!direct!photon!at!large!rapidity!!
!!!!to!test!a!gluon!satura'on!i.e.!Color!Grass!Condensate!

Components%!2!Electromagne'c!Calorimeter!:!FoCal2E!
!2!Hadron!Calorimeter!!!!!!!!!!!!!!!!!:!FoCal2H!

Acceptance%%%O!3.3!<!η!<!5.3!

Observables%!2!π0!→!2γ!
!2!direct(isolated)!photons!
!2!J/Ψ!(under!study)!
!2!Jets!(under!study)!

←FoCal2E!subjectFig.1!:!Installa'on!plan!of!Forward!CalorimeterFig.3!:!LGL!prototype!
(made!by!Oak!Ridge!Na'onal!Laboratory)

Fig.2!:!FoCal2E!strawman!design(yellow!:!HGL,!green!:!LGL)

Test%beam%resultsTest%beam%2014
Test%beam%at%PS%and%SPS!

Energy%linearity%of%PS%and%SPS

2!Test!beam!at!PS!beam!line!on!Sep!–!Oct!2014.!
!!!Beam!energy!is!2!~!10!GeV.!
!!!In!PS!beam!line,!we!can!iden'fy!the!electron.!
!2!Next,!test!beam!at!SPS!beam!line!on!Nov!2014.!
!!!Beam!energy!is!30!~!100!GeV.!

Noise%measurements
Pedestal%σ%[ch]

ADC[ch]

Condi'on!and!testbench!of!PS!and!SPS
PS!
!2!T9!beam!line!
!2!Term!:!Sep!–!Oct!in!2014!
!2!energy!:!2!~!10!GeV!
!2!beam!rate!:!100!Hz!
!2!gain!:!high!gain(1/1)
Cherenkov!:!iden'ﬁca'on!of!electron

Fig.4!:!testbench!at!PS

Beam%Energy[GeV]

Fig.8!:!energy!linearity!at!PS!and!SPS
SPS!
!2!T4!–!H8!beam!line!
!2!Term!:!Nov!in!2014!
!2!energy!:!30!~!100!GeV!
!2!beam!rate!:!300!Hz!
!2!gain!:!low!gain(1/16)

We!can!take!the!data!of!2!&!3GeV!at!PS!!
and!30!&!50GeV!at!SPS.!

Fig.5!:!testbench!at!SPSLGL%readout%system

We!can!see!the!energy!linearity.!
Next!test!beam,!cover!the!other!energies.

%apv_ch%[channel]

Fig.9!:!comparison!of!noise!for!each!varia'on
On!PS!experiment,!noise!is!large.!
We!try!decreasing!the!noise.

When!summing!board!is!ON(Low!voltage!ON),!!
pedestal!sigma!value!is!large!especially.!
→introduc'on!of!regula'on!power!supply.!
On!the!other!hands,!we!perform!op'miza'on!of!the!GND.

Shower%proﬁle

We!use!the!APV!hybrid!board!and!ADC!board,!FEC!board!as!electronics!of!
readout(Fig.6).!
These!electronics!is!developed!by!CERN!RD51!group.!
APV!chip!have!128!output!and!sampling!speed!of!APV!is!40MHz.!
ADC!board!has!simultaneous!readout!from!8!APV!hybrid!board!for!12!bit!ADC!
and!the!role!of!FEC!board!is!to!process!informa'on!from!ADC.!

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Readout!electronics!:!developed!by!CERN!RD51!group!
APV25!hybrid!board!
!2!output!:!128ch!
!2!sampling!speed!:!40MHz!
SRS(Scalable!Readout!System)!
!2!ADC!board!:!12!bit!ADC!
!!!Simultaneous!readout!from!8!APV!hybrid!board(Master)!!
!2!FEC!board!:!the!front2end!which!processes!informa'on!from!ADC

We!use!the!center!of!gravity!equa'on!to!study!the!shower!shape.!
By!calcula'ng!the!gap!of!beam’s!center!of!gravity,!we!can!see!the!shower!proﬁle.The!center!of!gravity!equa'on

Shower!proﬁle!equa'on

!s!!!!!:!which!LGL!
!i!,!j!:!!PAD!of!x!&!y!axis

beam!:!2GeV!electron!
Longitudinal!shower!proﬁle!
!2!shower!max!d!(for!W)!=!19.27mm!←!2nd!LGL!!
Transverse!shower!proﬁle!
!2!re2calculate!shower!center!(centroid)!
!2!Moliere!radius!(for!W)!:!9.16mm!
longitudinal!and!transverse!shower!proﬁles!are!
consistent!with!the!expecta'on!
!2!At!depth!17.5!–!28[mm],!expanse!of!shower!is!largeFig.10!:!Gap!of!center!of!gravity!for!the!hit
Fig.6!:!APV!hybrid!board!and!!
ADC!and!FEC!board!pictureSummary 22222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222
2 In!our!ﬁrst!test!beam!2014,!we!were!able!to!see!the!shower!proﬁle!and!energy!linearity.!
!!!!!2!We!can!see!the!2!and!3,!30,!50!GeV!beam!signal.!→!Observa'on!of!energy!linearity.!
!!!!!2!Shower!max!point!is!consistent!with!the!expecta'on.!←!2nd!LGL.!
!!!!!2!Op'miza'on!carried!out!to!reduce!noise!level.!For!example,!Op'miza'on!of!the!GND!and!!
!!!!!!!Introduc'on!of!stabiliza'on!power!supply.

Outlook
Fig.7!:!readout!ﬂow!chart

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2!Second!test!beam!scheduled!on!Oct!–!Nov!at!PS!and!SPS.!
!!!!!2!comple'on!of!energy!dependence!and!resolu'on!for!LGL.!!
!2!We!joined!RD51!group!and!started!work!of!new!readout!board!for!new!readout!system.!