# Presentation: 525339

## ALICE EMCal Electronics

- Outline:
- Design Specifications
- Why PHOS readout is suitable
- Necessary differences from PHOS
- Shaping time / data volume problem
- EMCal vs PHOS comparison summary
- Work ahead...

- Slides posted at http://www.phenix.bnl.gov/phenix/WWW/publish/awes/ALICE

## ALICE EMCAL

- Pb-scintillator sampling calorimeter
-  -0.7 <  < 0.7
-  degrees
- Energy resolution ~12%/√E

- 12 super-modules (each 2.8 x PHOS module)
-  projective towers
- Tower: x~0.014x0.014

-  Design goal: Maximize acceptance. It cannot be bigger! (34 x PHOS module)
-  Fixed budget limits granularity and resolution.

## Tower/module structure: “shashlik” design

**Tower/module structure: “shashlik” design**

- Total Pb depth = 124 mm = 22.1 X0
- Comparisons:
- PHOS = 180 mm/8.9 mm = 20.2 X0
- ATLAS LiqAr/Pb = 25 X0
- CMS  PbWO = 25 X0

- Trapezoidal module: transverse size varies in depth from 63x63 to 63x67 mm2
- 78 layers of 1.6 mm scint/1.6 mm Pb
- Moliere radius ~ 2 cm

- Pb absorber has dimensions of module

- Towers defined by smaller optically isolated scintillator tiles

- Going to Shashlik design allows to use thinner sampling layers to improve intrinsic energy resolution.

## EMCAL Physical Parameters

## inclusive jets

- 10 Hz @ 50 GeV

- few x 104/year for ET>150 GeV

- EFS = 250 GeV
- (PHOS 80 GeV)

**Full Scale energy...**

- From Peter Jacobs

## Use PHOS APD + Charge Sensitive PreAmplifier

-  Must operate in Magnetic Field.
-  Need gain (and gain adjustment for trigger)
-  Light yield from EMCal similar to PHOS

## Light yield

- Light Yield (in photo-electrons) measured at WSU with Cosmic rays in prototype tower using  well-calibrated PMT.

- For APD, with Gain M=1 expect ~2.5 photoelectrons/MeV
- Compare PHOS: 4.4 pe/MeV @ M=1. For same fullscale signal amplitude MEmcal = 50(MPHOS)*(4.4*80GeV)/(2.5*250GeV)=28

## Intrinsic Energy Resolution

- GEANT Simulation results:
- Sampling fraction 8.1%
- Intrinsic energy resolution ~12%

- Calculations by Aleksei Pavlinov

## The PHOS APD + CSP Electronic Noise

-  PHOS measurement 625e @ 2s shaping  : 625/(4.4*50)=2.8 MeV
-  If EMCal uses 100ns shaping, expect ~1500e  : 1500/(2.5*50)=12 MeV (36MeV 3x3)

- from PHOS Electronics Document

## Energy Resolution: All contributions

**Energy Resolution: All contributions**

- Even with pessimistic assumptions (eNC=2000) electronics contributions to
- resolution are unimportant in energy region of primary interest.
- Important open question: slow neutrons
-  drives choice to investigate short shaping time ~100 ns.

- 12% intrinsic

- 1% calibration

- Digitization
- (full scale=250 GeV)

- PA/shaper
- eNC=2000 (60MeV)

- Dual 10-bit ADCs (high and low gain)

## EMCal Resolution: The ALICE “Environment”

**EMCal Resolution: The ALICE “Environment”**

- EMCAL only

- All ALICE material

- GEANT Simulations for single photons (i.e. p+p)
- Significant degradation of resolution

- A. Pavlinov

## The ALICE “Environment”

**The ALICE “Environment”**

- Before 30ns

- After 30 ns

- Large background from moderately slow neutrons.

- Central HIJING Simulations: Production point of particles with EDeposit

- Calculations by Heather Gray

## Soft,Slow (neutron) Background

**Soft,Slow (neutron) Background**

- Calculations by Heather Gray

- Total EMCal EDeposit vs Time

- Tower  neutron EDeposit

- Mean neutron EDeposit =36 MeV (i.e. 3 times electronic noise!) with rms=41MeV
- Note: This is for Central HIJING (worse case, the problem is centrality dependent).

## Soft,Slow (neutron) Background

- Tower Cut
- 1 100MeV
- 2 150MeV
- 3 200MeV
- 4 500MeV
- Time Integ.
- 0 20ns
- 1 30ns
- 2 50ns
- 3 100ns
- 4 200ns
- 5 500ns
- 6 1000ns

- Calculations by Heather Gray

- Kill the number of neutron hits by tower threshold or (integration) time cut.

- Tower threshold cut of ~150MeV is effective, but it doesn’t remove neutron energy deposit in tower with real gamma hit!

-  Integration time cut can also reduce the number of neutron hits. Benefit also applies to tower with real hit.
- Note: Using PHOS cluster algorithm _without_ splitting.

## Soft,Slow (neutron) Background

**Soft,Slow (neutron) Background**

- Tower Cut
- 1 100MeV
- 2 150MeV
- 3 200MeV
- 4 500MeV
- Time Integ.
- 0 20ns
- 1 30ns
- 2 50ns
- 3 100ns
- 4 200ns
- 5 500ns
- 6 1000ns

- 10-20 GeV/c  + HIJING (b<3fm) Full ALICE

- Calculations by Heather Gray

- Tower energy threshold and integration time cuts are correlated.
- Shortening integration time allows to lower tower energy resolution, which will improve performance especially at low pT.
- Note: Using PHOS cluster algorithm _without_ splitting.
- Feasible to use a shaping time of ~100ns with PHOS electronics?

## Soft,Slow (neutron) Background

**Soft,Slow (neutron) Background**

- Calculations by Heather Gray

- The Alarming Plot...

- Taking the shower core only...

- Conclusion: Neutrons cause large occupancy - difficulty for cluster finding.
- Will need to use shower core with high tower threshold. Shorter shaping time will improve the situation.
- Again: This is for Central HIJING (worse case, the problem is centrality dependent).

- due to large clusters

## Bandwidth: Another shaping time argument

- Propose to use peak = 100ns with 20MHz sampling
- Ex: PHOS Bandwidth
- Number of samples = 5*peak/tsample = 5*4s/100ns = 200
- Average hit rate (>30MeV) = 200Hz
- GTL bus rate = (14FEE)(32chan)(2Gain)(10bit)(200samples)(200Hz)=44.8MB/s
- RCU data rate = 2*GTL/RCU partition=89MB/s (limit 100MB/s)
- EMCal Bandwidth
- Number of samples = 5*peak/tsample = 5*200ns/50ns = 20
- Average hit rate (>30MeV) = 2000Hz (from 6x6/2x2, or 80% occupancy in central Pb+Pb(GEANT) -> 25% min bias -> 2kHz)
- GTL bus rate = (12FEE)(32chan)(2Gain)(10bit)(20samples)(2000Hz)=38.4MB/s
- RCU data rate = 2*GTL/RCU partition=77MB/s
- If peak = 4s with 200 samples then GTL bus rate=384MB/s  - Death!

## EMCAL vs PHOS Readout Parameters

## FEE C-W Shaper Parameters

**FEE C-W Shaper Parameters**

- Definitions and values (1,2s) taken from PHOS electronics document (Thanks to Hans for excellent documention):

-  Would like confirmation (i.e. opinion of CW engineer) that the 100ns values are reasonble.
-  Then modify a PHOS FEE to use the 100ns values and test in laboratory.
-  If results look reasonable, then would like to use FEE with 100ns values in Testbeam at FNAL.

## EMCal L0 trigger input concerns...

- Upon receipt of L0, the ALTRO chip keeps 14 presamples:
- For PHOS with 10MHz sampling this is region of 1.4 s prior to L0.
- For EMCal with 20MHz sampling this is region of 700ns prior to L0.
- With ALICE L0 latency of 1.2 s
- For 10MHz sampling this is just okay with   ~no presamples
- For 20MHz sampling this is 300ns after 200ns peaking time - Death!
- Proposed PHOS solution is to use local PHOS L0 trigger output as ALTRO L0 trigger input. Would “solve” problem for EMCal also, but...
- This seems to be a very dangerous solution...
- L0(PHOS) .ne. L0(CTP): might have L0(CTP) without L0(PHOS) then L2 request when there was no L0...
- Danger of filling ALTRO buffer with noisely local L0’s?
- Only alternative for EMCal seems to be to keep 10MHz sampling and go to 200ns shaping time.

## PHOS vs EMCal Readout comparison

- Commonalities:
- Same APD + preamplifier
- Same GTL bus (maybe, maybe not identical?)
- ~Same FEE
- Same RCU,TRU, etc
- Differences
- Different T-Card:  FEE likely located far away, need signals driver on T-card+twisted pair?
- Same FEE but with shorter shaping time, 100ns?
- Altro sampling at 20 MHz?,  only 20 samples/gain/channel.
- Numerology, FEE to GTL to RCU, TRU
- New (later option) TRU’ to form larger area energy sums for jet trigger.
- Other
- Power consumption: 63mW*1152 = 73W in SM, 450W in FEE region of SM

## EMCal Electronics: Numerology

- APD+PreAmp

- Transition Card

- FEE-card w/ ALTRO

- 8

- 4

- TRU =
- Trigger Router Unit

- 36

- RCU =
- Read-out Control Unit

- 2 RCU/SuperModule = 1152 Towers (cf. 896 PHOS)

- Level 0

- Level 1

- 3  OR
- per SM

**EMCal Electronics: Numerology**

- 32 Channels

- 384  Towers

-    Towers
- (768       +   384)

- 12

- TRU’ =
- Trigger Router Unit’

- 36

- 13824    Towers

- Level 1

- , . .

## EMCal Jet Trigger (TRU’?)

**EMCal Jet Trigger (TRU’?)**

- Calculations by Bill Mayes

- Conclusion: Increasing trigger region requires in increase trigger threshold for same trigger rejection factor (e.g. central HIJING). Not much difference in trigger efficiency (on PYTHIA jets) versus trigger region size - except for large patch sizes.
- PHOS TRU size (4x4 tower)  works quite well...

## PHOS Module Assembly

**PHOS Module Assembly**

**FEE Card**
**32 Channels**
**35cm x 21cm**
**5.5 Watts (170mW/ch)**
**870SF (27SF/ch)**

## Slide 25

## EMCal Readout Matrix per Supermodule 

- Totals/SuperModule
- 36 FEE cards
- 3 GTL bus
- 3 TRU
- 1 RCU

- EMCal Readout Matrix per Supermodule

## EMCal Readout Joblist

- After hiatus, need to come “up to speed” to get EMCal requirements folded into ALICE infrastructure. E.g. Rack space, LV,trigger, DCS,etc.
- To first order, EMCal looks like PHOS (which we have relied upon heavily, thanks to Bernhard, Hans, etc)
- Clearer delineation of items EMCal vs ALICE responsibility to provide
- Critical item is to confirm acceptable performance with shorter shaping and fewer samples
- Testbeam planned for Nov at FNAL to use 8x8 tower array with PHOS electronics. Intend to test shorter shaping time (after demonstrating acceptable performance with PHOS shaping)
- Intend to build and instrument first Supermodule on R&D funds in time for first Pb run in ‘08.
- To the largest extent possible EMCal and PHOS should combine orders to obtain bulk discounts, and use the same modules to lower the necessary inventory of “spare” modules.
- EMCal and PHOS should work closely together to share resources, e.g. testing and code development (to mutual benefit!) and to insure that the subsystems appear as similar as possible to ALICE.

## http://www-ppd.fnal.gov/MTBF-w/mtbf_mou.htm

**List of MTBF Memoranda of Understanding (MOU):**
- _[ ](http://www-ppd.fnal.gov/mtbf-w/T926_mou.doc)__[T926: RICE](http://www-ppd.fnal.gov/mtbf-w/T926_mou.doc)_**   Experiment completed**
- _[ ](http://www-ppd.fnal.gov/mtbf-w/T927_mou.doc)__[T927:](http://www-ppd.fnal.gov/mtbf-w/T927_mou.doc)__[ BTeV](http://www-ppd.fnal.gov/mtbf-w/T927_mou.doc)__[ Pixel](http://www-ppd.fnal.gov/mtbf-w/T927_mou.doc)_**   Experiment completed**
- _[ ](http://www-ppd.fnal.gov/mtbf-w/T930_mou.doc)__[T930:](http://www-ppd.fnal.gov/mtbf-w/T930_mou.doc)__[ BTeV](http://www-ppd.fnal.gov/mtbf-w/T930_mou.doc)__[ Straw](http://www-ppd.fnal.gov/mtbf-w/T930_mou.doc)_**   Experiment completed**
- _[ ](http://www-ppd.fnal.gov/mtbf-w/T931_mou.doc)__[T931:](http://www-ppd.fnal.gov/mtbf-w/T931_mou.doc)__[ BTeV Muon](http://www-ppd.fnal.gov/mtbf-w/T931_mou.doc)_**   Experiment completed**
- _[T932: Diamond Detector](http://www-ppd.fnal.gov/mtbf-w/T932_mou.doc)_**   Signed**
- _[ ](http://www-ppd.fnal.gov/mtbf-w/T933_mou.doc)__[T933:](http://www-ppd.fnal.gov/mtbf-w/T933_mou.doc)__[ BTeV](http://www-ppd.fnal.gov/mtbf-w/T933_mou.doc)__[ ECAL](http://www-ppd.fnal.gov/mtbf-w/T933_mou.doc)_**   Experiment completed**
- _[ ](http://www-ppd.fnal.gov/mtbf-w/T935_mou.doc)__[T935:](http://www-ppd.fnal.gov/mtbf-w/T935_mou.doc)__[ BTeV](http://www-ppd.fnal.gov/mtbf-w/T935_mou.doc)__[ RICH](http://www-ppd.fnal.gov/mtbf-w/T935_mou.doc)_**   Experiment completed**
- _[ ](http://www-ppd.fnal.gov/mtbf-w/T936_mou.doc)__[T936: US/CMS Forward Pixel](http://www-ppd.fnal.gov/mtbf-w/T936_mou.doc)_**  Taking data**
- _[ ](http://www-ppd.fnal.gov/MTBF-w/T941_mou.doc)__[T941:](http://www-ppd.fnal.gov/MTBF-w/T941_mou.doc)__[ UIowa](http://www-ppd.fnal.gov/MTBF-w/T941_mou.doc)__[ PPAC Test](http://www-ppd.fnal.gov/MTBF-w/T941_mou.doc)_**  Experiment completed**
- _[  ](http://www-ppd.fnal.gov/MTBF-w/T943_mou.doc)__[T943: U. Hawaii Monolithic Active Pixel Detector](http://www-ppd.fnal.gov/MTBF-w/T943_mou.doc)_**  Experiment completed**
- _[ ](http://www-ppd.fnal.gov/MTBF-w/T950_mou.doc)__[T950: Vacuum Straw Tracker](http://www-ppd.fnal.gov/MTBF-w/T950_mou.doc)_**   Being signed**
- _[ ](http://www-ppd.fnal.gov/MTBF-w/T951_mou.doc)__[T951: ALICE EMCAL Prototype Test](http://www-ppd.fnal.gov/MTBF-w/T951_mou.doc)_**  **** In review**
- _[ ](http://www-ppd.fnal.gov/MTBF-w/T953_mou.doc)__[T953: U. Iowa](http://www-ppd.fnal.gov/MTBF-w/T953_mou.doc)__[ Cerenkov](http://www-ppd.fnal.gov/MTBF-w/T953_mou.doc)__[ Light Tests](http://www-ppd.fnal.gov/MTBF-w/T953_mou.doc)_**   In review  **

## EMCal Readout Cost & Schedule

- We have reasonable initial cost estimates from PHOS costs for first Module.
- Unfortunately, we missed inclusionof first SM order with PHOS order for  APD,preamp,FEE.
- Hopefully, this can be done for next PHOS modules...
- Need to confirm stock of ALTRO, RCU,..

## Additional Slides

## EMCAL Readout Parameters

## Slide 32

## Slide 33

## Slide 34

## PHOS FEE

-  9 Pre-production prototypes produced at Huaxiang University of science and technology.
-  Used in PHOS test beam period of Oct.’04).

## Slide 36

## Slide 37

## Slide 38

## Slide 39

## EMCAL: main jet physics capabilities

- Level 1 trigger for jets, 0/
- essential for jet ET>50 GeV
- Improved jet energy resolution
- charged-only jets: poor resolution (>50%)
-  TPC+EMCAL: resolution ~30%
- main effect: out-of-cone energy (R~0.3 for heavy ions)
- also: intrinsic resolution; missing n, K0L, 
- discrimination to pT~30-40 GeV (cross section limit for +jet coincidences in acceptance)

## Supermodules

- 0.0 < || < 0.7,  = 20o

**Supermodules**

## Tower granularity (cont’d)

**Tower granularity (cont’d)**

- 0 opening angle

-  shower shape discrimination

- Heather Gray, LBNL/Cape Town

- 

- 

- rejection for pT<~30 GeV/c

- More sophisticated SSA underway, possible large improvements
- Additional +jet issues:
-  other backgrounds: fragmentation , radiative decays, ...
-  isolation cuts

- +jet is important but limited measurement
-  fixed $$$: maximize acceptance for jets, granularity driven by cost

- preliminary