Status report on ECAL

Status report on ECALStatus report on ECAL

TIM , Houston 8-12 Jan 2007

Marco Incagli - INFN Pisa

for the ECAL group

Marco Incagli - INFN Pisa 2

International ECAL collaboration

IHEP Beijing, China (Group Leader : Hesheng Chen)

LAPP Annecy , FranceFrance (Group Leader: JP Vialle)

INFN Pisa, Italy (Group Leader : F Cervelli)

Project responsible : F. Cervelli


Where is ECAL

Last detector crossed by incoming (downgoing) particlesThick detector in which particles interact in a destructive way

Minimum amount of material (X0):

Upper TOF

Tracker Entry

Tracker Exit

ECAL Exit

0.2

0

0.2

8

0.3

2

0.4

0

16

.5Tracker Total

0.0

4

ECAL Entry

ECAL Total

16

.1


ECAL = Electromagnet CALorimeter

A CALorimeter is a thick chunk of material in which particles deposit (part of) their energy (CÁLOR=heatenergy)

Most ground based experiments have large calorimetric systems

CMS


Some advantages of calorimeters

Resolution improves with the particle energy, differently from trackers in which resolution momentum

Energy loss due to finite dimensions scales with the logarythm of the particle energy (therefore very slowly)

fit

)%..(E

)%..(1062

50610

E

En

ergy

res

olu

tion

(%

)

50 GeV e-

En

ergy

dep

osit

ed (

GeV

/lay

er)

Longitudinal layer number


Disadvantages of calorimeters

They are heavy!Very different interaction cross sections for “light particles” (photons, electrons, positrons) wrt “heavy particles” (protons, deuterons, nuclei)Often, in ground experiments, 2 calorimetric sections are foreseen

ECAL : electromagnetic section

HCAL : hadronic section

CDF @ Fermilab


Calorimetry in space

due to limitations in weight, space experiments have just an ECAL section, normally with limited thicknessStandard measurement for “thickness” is the radiation length (X0) which is related to the development of the energy deposition by a particle a detector with high X0 has a good energy and angular

resolution and it is capable of measuring particles in the energy range 10GeV-1TeV with good accuracy (<5%)

e.g. : AGILE : 1.5X0 GLAST 10X0 AMS-02 : 16.1 X0


AMS ECAL

Thanks to the characteristics of the ISS (and of the Space Shuttle) AMS02 can take advantage of a calorimeter of unprecedented thickness and granularity, for space standards

1. Very good positron/proton discrimination

2. Good energy reolution for positrons and photons up to ~1TeV

3. Detection of photons non-interacting in material above (~75% of the total)

4. Discrimination of nuclei Z by energy deposition

5. Trigger information on photons and on e±

e+, p ?

Physics with ECAL


Dark Matter searches in positrons

~30% of the universe is made of matter of unknown origin: DARK MATTER

Most theories predict a surplus in the production of positrons, due to DARK MATTER

Hints from HEAT and AMS-01

AMS-02 can measure this distribution with very small statistical error (<0.1%) … BUT …


…background subtraction

…BUT… what about systematic error?A particular concern is the “background subtraction”Proton flux higher by 104 ; to measure positrons at 1% need suppression factor of 106 TRD provides a factor 102:103

The ECAL standalone provides a factor 103

Including the energy-momentum match, a further factor 10 is gained

protons

positrons


Photons can be detected in AMS field of view by two devices

TRACKER: uses conversion in 0.25X0 TRD material (max opening angle ~40o; conversion probability ~18%)

ECAL: uses the shower shape and asks for no hits in TOF counters (opening angle ~20o ; ~78% of the photons reach ECAL)

e+ e-

ECAL structure • Sampling calorimeter with lead foils and scintillating fibers

• Basic block is superlayer: 11 lead and 10 fiber layers

• 9 superlayers with alternating x and y readout

• Total thickness is 166mm, corresponding to 16.2 X0

• Total weight 634 kg

Lead foil(1mm)

Fibers(1mm)

y x

z particle direction1.73mm

p e

FIBER

LEAD


Supporting structure and readout of AMS ECAL

18.5 mm

• The active part is inserted in a supporting structure which connects ECAL to USS

• Light is readout with PhotoMultiplierTubes (PMTs) connected to fibers through light guides

yx

z66 cm


Pictures of ECAL production

ECALECAL


Status of construction in short

Flight hardware: detector : ready front end electronics : ready and mounted on detector readout electronics : QM tested, FM under construction,

ready by end of April 2007 (boards + mechanics) must undergo SQ tests (vibration + thermo-vacuum)

HV power supply : ready except for heaters and thermostats

must undergo SQ tests (vibration + thermo-vacuum) LV power supply : under construction in Taiwan


Detector + front end electronics

Completed in September 2006

Tested in CERN North Area experimental hall Oct 15-30 with protons of 150GeV and electrons of 6-210 GeV

Currently stored in class 100K clean area


Readout electronics : FM

Production started november, 2006 Check of drawings : ok Check of material :

PCBs all done Electrical components all in stock except for few

connectors to be soldered on ECAL Back Plane (EBP) Mechanical parts front panels done and anodized;

to be treated with alodine for conductivity. Crate production in Pisa: Feb,1 May,1 . Surface treatment (white paint): May,1 May,15


3 EBP (backplane), 2FM+1FS , mounted and inspected to be tested in Pisa

All electronics ready by end of April


HV power supply

Flight HV ready and mounted on temporary stand

Missing parts: heaters (2) thermostats (4) reflecting tape

Offer requests sent this week to CGS 3/4 months for delivery


LowVoltage: ERPD crate

FM

•Electronics:

• DC/DC were tested in Taiwan by J. Marin.

• Board with failures repaired by CAEN now at CIEMAT (Madrid).

• Ready to be sent to Taiwan for final test and coating.

•Mechanics:

• Items 5,6,7 ready

• Material for the rest of items 1,2,3,4 sent to IAC.


ECAL test beam

ECAL FM has been mounted on a frame and equipped with FM or QM electronics; work done at LAPP, Annecy (FR) on sep-oct 2006

ECAL mounted on rotating table and carried to CERN


ECAL at test beam

ECAL in the test beam area covered to protect flight hardware (color chosen by Sylvie…)

Incoming beam


Not only ECAL test beam

Cherenkov countersTrigger countersTracker:4 ladders

ECALEcrate 0

Ecrate 1NIM crate

NIM LVDS

PCI AMSWIRE

JTCRATE

JLV

1

JIN

J

JTB

OX


A complex DAQ system

JLV1

ETRG

8 AMSWire cables10 m long

PCI-AMSWIRE

External Trigger

EthernetCable50 m

E0-crate E1-crate T-crate

JT-crate

JINF

ETRG

JINF

JINF

JTBX

JINJ

EPPCAN

Linux PC

PARALLEL PORT

E T SH WE IR TN CE HT

• Software for readout written by Stefano Di Falco with the help, or based on the programs, of P.Azzarello (Perugia), D.Haas (Geneve), A.Kounine (MIT), A.Lebedev (MIT)• Request from Helsinky University of Technology (Finland) to provide raw data taken at test beam in order to test data transfer with real AMS data

2 AMSWire cables


Trigger system : rather elaborate!

Fast trigger window: ECAL,

counters, Cherenkov

“TOF” window: used by external

scintillator counters

Level 1 window

Internal oscillator: pedestals

evaluation (asynchronous

trigger)


To “calibrate” ECAL means to know its response to an impinging particle of known energy

We use “Minimum Ionizing Particles” (MIPs) : hadrons, tipically protons, or muons (cosmic rays at sea level) which cross ECAL without interacting with the lead nuclei but just with the external electrons of the material

Trajectory and energy of MIPs are marginally modified by this process: a MIP proton deposits 0.125GeV crossing ECAL.

MIP

Main goal of test beam: ECAL calibration


Proton runs with 20k events along y and x axisEach run hits the center of a PMT columnTotal of 72 runs per each cross (12 hours of data taking)4 MIP scans:

o Nominal voltageo Nominal voltage+50Voltso Nominal voltageo Nominal voltage+80Volts

Changing voltage varies signal amplification

MIP cross scan

5 rows

4 ro

ws

y

x


MIP distribution

Typical distribution of energy deposited by a MIP in an ECAL cell, in ADC counts, fitted with a Landau distribution

The different peak position reflects the different voltage (=amplification)

Note that a too large amplification limits the dynamical range of the amplifier

Nominal HVPeak = 17.2 ADCcounts

Nominal HV + 50VoltsPeak = 32.7 ADCcounts


Mip distribution

MIP peak (ADC counts)

Problem in “zero suppression” algorythm

We know how to fix this software problem; new software tested with cosmic rays


Beam profile using tracker layers

4 tracker ladders, in front of ECAL, have been used to measure the beam profile and to know the particle hit position event by event

The beam profile changes with particle type (electrons vs protons), beam energy, primary beam polarity, …

Beam dimensions ~2×2cm2; each strip is ~100m

BLACK = 3 laddersRED = 4 ladders

BLACK = 3 laddersRED = 4 ladders

1 cm

1 cm


Tracker-ECAL correlation

0.9cm : ECAL cell size

Beam profile : xview Beam profile : yview

EC

AL

cel

ls


Testing the trigger

ECAL trigger ANALOG part on ECAL Intermediate Board (EIB)

DIGITAL part (=trigger logic) in ETRG board

+

-10 +

-comp

thresh

FF

D Q1RPMT dynode

EIBto ECAL crate

OutputSignal

from PMT Programmablethreshold


Test of analog part of trigger

Trigger efficiency as a function of deposited energy in single cell

Varying the programmable threshold, the trigger threshold moves

Deposited energy (ADCcounts)

100

80

60

40

20

0

Eff

icie

ncy

(%)

Trigger threshold

Trigger threshold

Trigger threshold


Electron runs

Electron can release, in a given cell, an amount of energy which is several thousands larger than that of a MIP

In order to cover the full energy range, the signal is split in 2 and 1 branch is divided by a factor ~30 before ADC

PMT cellHigh gain

Low gain

Z

Y

X

PMT (PhotoMultiplier Tube)


High gain vs low gain

We expect a straight line, but on some cells we see a spurius population under study

Hig

h G

ain

Low Gain

Hig

h G

ain

Low Gain


Linearity plot : ADC counts vs beam energy

As a consequence Anode ADC counts vs

energy shows 2 slopes, up to 30GeV and from 50GeV up . No corrections for energy leakage applied

Linearity plot with dynode (again no corrections) shows a linear behaviour

Under investigation


Conclusions

ECAL ready for integration

FM electronics in production; ready end of April 2007 need to do SQ tests for all crates (Ecrate+HV+LV) !

Test beam shows good results in terms of MIP (protons) analysis;

some unclear results for more energetic (tipically electrons) energy deposits under investigation

very useful to debug and calibrate flight hardware and firmware ; positive test of trigger system and of DAQ procedure

More results at next TIM

BACKUP SLIDESBACKUP SLIDES


Problems in zero suppression

In order to limit the bandwidth, only channels with an ADC count value above some limit (>2 in our case) are written out

This procedure is called zero suppression and it is authomatically run at the beginning of each data taking

Due to the large beam rate, some times a spurius event enters in the evaluation of the pedestal shifting its value

SMALL pedestal shiftDistribution cut at 9 ADC countsFit is still possiblePeak = 17.5 counts

LARGE pedestal shiftDistribution cut at 26(!) countsFit is not possiblePeak = ?


Mip distribution

We know how to fix this software problem; new software will be tested with cosmic ray runs

The effect is uncorrelated with the PMT number, so >90% of ECAL cells (1324 in total) have been equalized using the two scans at nominal voltage

MIP peak (ADC counts)

Remaining channels can be equalized with ground level cosmic rays (muons instead of protons, but same properties for equalization)

Documents

Status report on ECAL