A MAPS-based readout for a Tera-Pixel electromagnetic calorimeter at the ILC

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1 A MAPS-based readout for a Tera-Pixel electromagnetic calorimeter at the ILC STFC-Rutherford Appleton Laboratory Y. Mikami, O. Miller, V. Rajovic, N.K. Watson, J.A. Wilson University of Birmingham J.A. Ballin, P.D. Dauncey, A.-M. Magnan, M. Noy Imperial College London J.P. Crooks, B. Levin, M.Lynch M. Stanitzki, K.D. Stefanov, R. Turchetta, M. Tyndel, E.G. Villani STFC-Rutherford Appleton Laboratory

2 The ILC 2625 ILC calorimetry focused on Particle Flow Approach (PFA) Requirement of highly granular calorimeters Goal : Jet Energy resolution ~ 30 % / E ILC environment is very different compared to LHC Bunch spacing of ~ 300 ns (baseline) 2625 bunches in 1ms 199 ms quiet time Occupancy dominated by beam background & noise 2

3 What are Particle Flow Algorithms (PFA)? Track reconstruction Calorimeter Clustering Match Tracks with Calorimeter Clusters Charged particles Remove associated Calorimeter Clusters Remaining EM-only Calorimeter Clusters Photons Remove Photon Calorimeter Clusters Remaining Calorimeter Clusters Neutral Hadrons DONE 3

4 SiW EM Calorimetry The baseline for the SiD & ILD detector concepts Sampling Calorimeter ECAL MODULE Silicon sensors embedded in tungsten sheets 30 layers meters radius COIL HCAL m2 silicon area Analog read out (4x4-5x5 mm pixels) Compact, has to fit inside the coil 4

5 Increasing the granularity PFA based on track-shower matching clear shower separation Granularity of 5x5 mm may not be sufficient for e.g. π0 identification from τ decays shower separation in dense jets Digital Pixels with 50x50 microns basically a Particle Counter requires highly integrated sensor ideal for MAPS-> TPAC design but 1 TeraPixel system... 5 τ decay

6 TPAC Sensor requirements Sensitive to MIP signal Pixels determine hit status (binary readout) Store bunch crossing number & location of hits Target noise rate 10-6 per Bunch crossing Design to buffer data for up to 8192 bunch crossings Readout in quiet time Masking & trimming individual pixels Minimize dead space 6

The INMAPS process Standard 0.18 micron CMOS Used in the TPAC 1.0 sensor 6 metal layers Analog & Digital @ 1.8 V & 3.

active circuits in the pixel Should reflect charge, preventing unwanted loss in charge collection efficiency Device

7 The INMAPS process Standard 0.18 micron CMOS Used in the TPAC 1.0 sensor 6 metal layers Analog & 1.8 V & 3.3 V 12 micron epitaxial layer Additional module: Deep PWell Developed specifically for this project Added beneath all active circuits in the pixel Should reflect charge, preventing unwanted loss in charge collection efficiency Device simulations using TCAD confirm shielding effect Test chip processing variants TPAC 1.0 manufactured with/without deep p-well for comparison 7

The TPAC 1.0 Sensor Four columns of logic + SRAM of which 11.

timestamps Local SRAM 0 1 2 Sa mp ler Pre 8.

variants Main variants PreShaper and PreSampler Minor variants

8 The TPAC 1.0 Sensor Four columns of logic + SRAM of which 11.1% dead (logic) Logic columns serve 42 pixels Record hit locations & timestamps Local SRAM Sa mp ler Pre 8.2 million transistors pixels (168 x 168) ; 50 microns; 4 variants Main variants PreShaper and PreSampler Minor variants Capacitor variants Sensitive area 79.4 mm2 P re Sha per 3 Data readout Slow (<5Mhz) 30 bit parallel data output 8

PreShaper variants only the PreShaper worked well in the array Deep p-well subtle changes

9 TPAC Architecture Details The two main variants PreSampler problematic in array PreShaper 4 diodes 1 resistor (4 MΩ) Configuration SRAM & Mask Comparator trim (4 bits) Two PreShaper variants only the PreShaper worked well in the array Deep p-well subtle changes to capacitors Predicted Performance Gain 94 μv/e Noise 23 e- Power 8.9 μw Diodes Circuit N-Wells 9

Sensor testing Test pixels presample pixel variant Analog output nodes IR laser stimulus (1064 nm) 55Fe stimulus quad0 Single pixel in array preshape

10 Sensor testing Test pixels presample pixel variant Analog output nodes IR laser stimulus (1064 nm) 55Fe stimulus quad0 Single pixel in array preshape (quad0/1) Per pixel masks IR Laser Stimulus (1064 nm) 55 Fe stimulus quad1 Full pixel array preshape (quad0/1) Pedestals & trim adjustment Gain uniformity Crosstalk 10

11 Analog Test Pixel : Laser Using 1064 nm Laser back-illuminate through substrate 2x2 μm spot, 2 μm steps Take Profile through 2 diodes in test pixel 11

12 Analog Test Pixel: 55 Generates 1640 e If a photon hits a diode 5.9 kev photon All energy deposited in approx 1 μm3 silicon Fe Fe main decay 55 no diffusion Absolute Gain calibration 12

13 Array : Pixel Response to laser Use same laser setup as for analog scans Single active pixel with/without laser firing Fire Laser at fixed point in pixel Threshold Scan with and without Laser Plateau due to memory saturation 13

14 Array : Single Pixel comparison Amplitude results from Laser Scan With/without deep p-well Compare Simulations GDS Measurements Real Pixel profiles F B 14

15 Array: Single Pixel 55 Fe response use Do a threshold Scan Need the derivative to reconstruct 55 Fe source on Pixel Array 55 Fe peak Derivative approximated using bin subtraction Single active pixel with/without source 15

16 Array: Pixel Noise Threshold scan required to see pedestal and noise Comparator fires on signal going high across threshold level No hits when far above or below threshold Width of distribution equivalent to noise RMS ~ 5.5 Threshold Units (TU) ~ 44 e ~ 170 ev on average Minimum is ~ 4 TU ~ 32 e ~ 120 ev Target level was ~ 90 ev No correlation with position on sensor Spread not fully understood Quad1 ~ 20% larger than Quad0 16 Threshold

17 Array: Pedestal adjustments Plot the distribution of pedestals Mean of Noise Calculate necessary trim adjustment Per-pixel trim file uni-directional adjustment Mean (TU) Re-scan pixels with trims Trim=0: Quad0; Quad1 Trimmed: Quad0; Quad1 Re-plot the distribution of pedestals Planned to have pedestal width ~ ½ Noise width have more trim bits Mean (TU) 17

Array: Pixel Gain Use laser to inject fixed-intensity signal into many pixels GAIN Quad0; Quad1 Relative position should be equivalent for each pixel

18 Array: Pixel Gain Use laser to inject fixed-intensity signal into many pixels GAIN Quad0; Quad1 Relative position should be equivalent for each pixel scanned Adjust/trim for known pixel pedestals Results Gain uniform to 12% Quad1 ~ 40% more gain than Quad0 Quad1 ~ 20% better S/N than Quad0 18 Threshold

19 Array Pixel Cross-talk Scan one pixel in the column, all others off. scan entire pixel column Effect of all pixels (other than the one being scanned) is to increase the general noise around zero. Shared power mesh between comparator and and monostable prime culprit, will be fixed 19

20 Future Plans TPAC 1.1 Have received TPAC1.1 a week ago Only one pixel variant (preshaper quad1) Upgrade trim adjustment from 4 bits to 6 bits Compatible format: size, pins, PCB/DAQ etc. Minor bugs fixed (e.g. cross-talk) Additional test pixels & devices for further process characterization 20

21 Conclusion TPAC 1.0 has been a success See response to Laser, Proved deep p-well approach for MAPS Only minor problems found Finishing characterization TPAC 1.1 Fe 55 will be evaluated in the upcoming months We plan to make full-reticle size sensor after that 2.5 x 2.5 cm 21

MAPS-based ECAL Option for ILC

MAPS-based ECAL Option for ILC, Spain Konstantin Stefanov On behalf of J. Crooks, P. Dauncey, A.-M. Magnan, Y. Mikami, R. Turchetta, M. Tyndel, G. Villani, N. Watson, J. Wilson v Introduction v ECAL with