# Presentation: 611479

## Silicon Tungsten CalorimetersThe WIZARD experiments– PART II –

- OUTLINE
- The PAMELA Si-W calorimeter electronics
- Developments for future space calorimeters
- FE electronics for the NCC: considerations

**G. Zampa, M. Boezio, V. Bonvicini, E. Mocchiutti, A. Vacchi, N. Zampa**
***(INFN-Sezione di Trieste, Italy)***

## The PAMELA Si-W Calorimeter

- Extraction of the antiproton signal from the background of electrons and identification of the positrons from the proton background
- Rejection factor* *better than* 10** 4** *with a selection efficiency  *> 90%*
- Measurement of the electron’s and positron’s energy with a resolution better than 10%
- Three-dimensional reconstruction of the
-    spatial development of the showers

- Modular sampling Si-W calorimeter with high granularity (W thickness *2.6 mm*,  *0.74 X**0*)
- Transverse segmentation: ≈ *2.4 mm* strip pitch
- Si detector: *8x8 cm**2*, *380 μm* thick
- Sensitive area: *24 x 24 cm**2*
- Total Depth: *16.3 X**0*, *0.6 ****0*, *22* layers Si-X/W/Si-Y
- Total number of channels: *4224*
- Self-trigger to study the electronic component up to *2 TeV*→ geometric factor *600 cm**2**sr*,* 30* times larger than PAMELA

## The calorimeter will operate in orbit  radiation environment:

Total Ionizing Dose: 3 krad inside the PAMELA container

Possible Single Event Effects: LATCH-UP and UPSET (digital logic)

Therefore:

         commercial electronic devices tested up to 30 krad

    fault tolerant design and use of redundancy

Data storage allocated for PAMELA: 10G byte per day

expected average trigger rate of 12 Hz
more than 40000 read-out channels

Digital processing to:

Compress the event data

Reduce the trigger rate discarding non interesting events

- Total Ionizing Dose: 3 krad inside the PAMELA container
- Possible Single Event Effects: LATCH-UP and UPSET (digital logic)
- Therefore:
-  **     **   commercial electronic devices tested up to 30 krad
-     fault tolerant design and use of redundancy
- Data storage allocated for PAMELA: 10G byte per day
- expected average trigger rate of 12 Hz
- more than 40000 read-out channels
- Digital processing to:
- Compress the event data
- Reduce the trigger rate discarding non interesting events

- Calorimeter electronics: requirements

- > 80G byte every day

## The CR1.4P: requirements & design specs

** **_**Circuit design specs**_**:**
** ****- Supply****	****	****	****	****	****	****  +/- 5 V**
** ****- Number of channels/chip****	****	****	****	****  16**
** ****- Maximum power consumption****	****	****	****  ****	****  100 mW/chip**
** ****- 1 MIP****	****	****	****	****	****	****  4.9 fC = 30500 e****-**
** ****- Linear dynamic range****	****	****	****	****  1400 MIPs**
** ****- Maximum output signal****	****	****	****	****  7 V**
** ****- Sensitivity****	****	****	****	****	****  5 mV/MIP**
** ****- Maximum detector leakage current****	****	****	****  100 nA**
** ****- Peaking time****	****	****	****	****	****  1 ********s**
** ****- Detector capacitance****	****	****	****	****  180 pF**
** ****- ENC****max**** @ 180 pF****	****	****	****	****	****  3000 e****-**** rms**
** ****- Integrated calibration capacitance****	****	****	****  2 pF**
** ****- Logic levels****	****	****	****	****	****  0/+5 V TTL**
** ****- Channel-to-channel pedestal variation****	****	****	****  +/- 50 mV**
** ****- Chip-to-chip pedestal variation****	****	****	****  +/- 100 mV**
** ****- Readout speed****	****	****	****	****	****  0.5 ********s/channel**
** ****- Output load****	****	****	****	****	****  20 k********//25 pF**
** ****- Counting rate****	****	****	****	****	****  30 kHz**

** ****Low power budget available (**_**50 W for CALO!**_**)**
** ****Measure interactions of very high energy particles**
** ****Measure non-interacting particles with high precision**
** ****Large detector capacitance, C****D**** ******** 180 pF**

**Low power cons.**

**> 1000 MIPs range**

**At least 8:1 on 1 MIP**

**Low noise slope**

## The CR1.4P: general architecture

**Architecture of a single channel of the CR1.4P**

** ****Alcatel/Mietec 2 um mixed A/D CMOS;**
** ****Input calibration ciruit;**
** “****Folded cascode” CSA;**
** ****C****f**** = 8 fF;**
** ****PMOS charge reset;**
** ****CR-RC shaper, 1 ********s peaking time;**
** ****T/H circuit + buffer;**
** ****Output MUX;**
** “****X2” output stage with DC bias;**
** ****Self-trigger circuit (not shown here)**

**R&D phase from 1996 to 1998 (3 different prototypes tested)**
**10 wafers (about 1300 chips) produced between 1998 and 2000**
**Total yield > 70%**
**264 chips equip the FM of the PAMELA Calorimeter**
**Adopted also by the PAMELA TRD**

## Slide 6

## Linearity and dynamic range

**CR1.4P**

**Max. deviation from**
**linear fit < 2.5 %**
**average linearity**
**better than 1 %**

**sensitivity 5.1 mV/MIP**
**R****f****(CSA)=630 k******

***Linearity and dynamic range***

**Linear dynamic range**
**1400 MIPs or 7 pC**

## Noise

**CR1.4P**

**Measured noise**
**2765 e****-**** rms + 4.7 e****-****/pF**

***Noise***

## Performance in operational conditions

***Performance in operational conditions***

**MIP signal from cosmic muons, Gaussian + Landau fit, ****S/N ******** 9/1**
**Data taken during pre-integration tests of the FM Calorimeter**

## Cross-talk items

**Cross-talk effects (occurring in both the detector and the electronics) of different origins become important**
**in case of very large charge deposits and should be accounted for.**
**3 different “cross-talk” effects:**
**Coherent negative in the detector ****(through the bias-ring), linearly with deposited energy, ****~ - ****0.5%**
**Coherent negative in the chip ****(through the bias circuitry of the shapers), linear with deposited energy, ****~ - ****0.5%**
**Positive on the two closest-neighbour strips ****(“classical” cross-talk) ****~ ****1%**

**Before correction**

**After correction**

**Example (data from June 2002 CERN SPS test beam): **

## CR1.4P self-trigger option

**These events are quite rare compared to the normal event rate of**** ****PAMELA**
**  ****important to have a large geometric factor to collect a**** ****reasonable statistics during**
**  ****the 3-year estimated mission lifetime**
**Using the calorimeter “stand-alone” can extend the geometric factor of**** ****PAMELA**
**  ****from 21 cm****2****sr to ≈ 600 cm****2****sr, therefore:**
** **_**T**__**he CR1.4P was provided also with a “self-triggering” option**_

**Simplified block scheme of the self-trigger circuit in the CR1.4P**

***CR1.4P self-trigger option***

## Detector boards

- AD977A Analog Devices ADC
- Resolution: 16 bit
- Conversion time: 5 μs
- Power consumption: typ. 60 mW
- Serial data interface

**HOUSE KEEPING**
**CIRCUITS**

- Latch-up detection circuitry and power supply bus isolation capability
- FPGA: redundant scheme to minimize SEU (triple voting mechanism)
- Short-circuit protection of all common digital signals

## DAQ system

- A54SX72A Actel FPGA
- Logic gates: 72000
- I/O pins: 171 (PQFP208)
- Utilization: 70%

- ADSP2187L Analog Devices DSP
- Program memory: 16k Words (24 bit)
- Data memory: 16k Words (16 bit)
- Computational power: max. 52 MIPS
- Multi-function instructions
- Host interface to access internal memory

## Developments for futurespace calorimeters

-                                     → radiation tolerance
-                                     → low power consumption → low voltage CMOS
-                                                   → large acceptance → large # of read-out chan.
-                                                     → A/D converter integrated in the FE-ASIC

- KEY ISSUES:
- Space environment
- Satellite constraints
- Rare events (1 part./m2year)
- Dynamic range ≥ 10000 MIPs

- Developments for futurespace calorimeters

- Future astroparticle physics satellite-borne experiments will probe the cosmic rays spectrum at energies up to 1016 eV (“knee” region)
- Depending on the instrumentation that will be used, energy deposits between 105 MIP (NUCLEON) and 106 MIP (ACCESS) are expected in a readout channel
- CASIS R&D project: Si detectors and front-end ASICs for high-energy calorimetry in space

## Innovative Front-End architecture

- ADVANTAGES:
- A high default gain maximizes SNR for 1-MIP signals
- The modulator is insensitive to gain switch transients
- The modulator efficiently filters the electronic noise (resolution set by the over-sampling ratio)
- Several possible filter implementations: ASIC, FPGA and DSP

## New silicon detectors

**Gain CSA****1**** = 100 CSA****2**

## FE electronics requirements

Is CR1.4P suitable?

Possible alternative solution

- Is CR1.4P suitable?
- Possible alternative solution

- FE electronics for the NCC:considerations

## FE electronics requirements

- Dynamics: 500 MIPs
- SNR: ~10 for 1-MIP signals
- Si detectors: *6x6 cm**2*, *300 μm* thick, segmented in a *4x4* matrix of *1.5x1.5 cm**2* pixels
- Pixel capacitance: ~60 pF
- Readout rate: 10 MHz
- Readout channels: individual pixels, passive summation?
- Digitization: every clock or after LVL1 accept ?
- LL1 trigger: which kind of information from NCC ?

## Is CR-1.4P suitable?

- Dynamics of 1400 MIPs is a bit too high, but gain is good for a 12 bit ADC with a range of 2.5V
- The outputs of the 16 channels are multiplexed
- Maximum rate of about 10 kHz (can be improved a bit at the cost of higher noise)
- Self-trigger system works only for large signals and requires a gating signal
- Pedestal dependence on temperature (1 MIP/°C) and on total input signal of the chip

- NCC requires a new FE ASIC → a different architecture is strongly suggested

## Possible alternative solution

- Charge Sensitive Amplifiers with dynamic range of 2500 MIPs
- Correlated Double Sampling at RHIC clock, dynamic range of 500 MIPs
- Clocked comparator at the output for LL1 trigger system

- Reuse as much as possible what already exists: AMU/ADC32
- Alternatively, real-time digitization with external ADCs and digital memory
- If not enough space for the electronics near the calorimeter, consider the integration of 12 bit pipeline ADCs (one per channel)

- Architecture of the proposed new FE ASIC (32 channels ?):

## Extra slides Results obtained with the calorimeter

## Second level trigger

- Aim: use the anticoincidence (AC) signal to reduce the trigger rate
- Problem: backscattering of particles in the calorimeter

- false trigger reduction ***70%*** at 95% of efficiency, estimated  trigger rate of ~***5 Hz***

## Baseline variations

detectors biased through a forward polarized p-n junction operating below threshold → high impedance toward the power supply → undesired injection in all strips through their junction capacitance
CR-1.4P: common bias of all shapers with poor output impedance→ change in the bias voltage → undesired signal in all channels 

Linear model:

- detectors biased through a forward polarized p-n junction operating below threshold → high impedance toward the power supply → undesired injection in all strips through their junction capacitance
- CR-1.4P: common bias of all shapers with poor output impedance→ change in the bias voltage → undesired signal in all channels
- Linear model:

- Calorimeter calibrations

- SNR = 8.6 ± 0.3

- Conversion gain

**Test beam**
**50 GeV/c protons**

## Baseline variations: model results

- Parameters distributions

**(mip)**

**(mip)**

- Linearity

## Energy measurement

- Test beam ***2**=0.055*, simulations ***2**=0.061*
- Expected resolution of the fully equipped calorimeter:  ≤*5% *in this energy range

**Data taken during test beam at CERN SPS, June 2002, with Calorimeter FM**

**Test beam**
**Simulations**

**Test beam**
**Simulations**

## Particle identification

- Efficiency *95%*
- Rejection factor *3**·10** 4*
- (8 protons out of 250000
- misidentified as electrons)

**Data taken during test beam at CERN SPS, June 2002, with Calorimeter FM**

## Self-trigger system test

- Front-end trigger time response depends on signal amplitude → time coincidence to reduce delay spread (*± 150 ns* is the max. allowed jitter for a sampling error *< 1%*)
- Simulations to define system parameters:
- Active trigger layers: from *4th* to *9th*
- threshold = *150 mip                                        **→ *trigger rate = *10 mHz*
- Coincidence window = *90 ns*
- Self-trigger signals of the calorimeter sections logically OR-ed

| particle | p 
[GeV/c] | measured
efficiency | simulated
efficiency |
| --- | --- | --- | --- |
| e- | 100 | 0.172 ± 0.004 | 0.236 ± 0.007 |
| e- | 150 | 0.679 ± 0.008 | 0.986 ± 0.002 |
| e- | 180 | 0.888 ± 0.005 | 0.990 ± 0.002 |
| e- | 300 | – | 0.994 ± 0.007 |
| p | 100 | (2 ± 1)·10-4 | (6.3 ± 0.8)·10-3 |
| p | 150 | (1.3 ± 0.2)·10-3 | (25 ± 2)·10-3 |

- Delay@*100GeV/c* *530 ns*, asymptotic value
*430 ns* → the signal sampling is accurate