A TARGET-based camera for CTA

TeV Array Readout with GSa/s sampling and Event Trigger (TARGET) chip: overview Custom-designed ASIC for CTA, developed in collaboration with Gary Varner (U Hawaii) Implementation: Switched capacitor array for waveform sampling Integrated digitization and trigger circuits Basic properties: High channel density (16 channels per chip) Deep analog memory (16,384 cells per channel for 16 µs at 1 GSa/s) Self-triggering (4 trigger channels per chip: each is analog sum of 4 input channels) Trigger mask for each of 16 channels (in case of noisy channels) 2

in numbers Requirements: Waveform sampling at ~1GHz Signal bandwidth > 380 MHz Cross-talk < 1% Look-back time: 16 μs Dynamic range: > 9 bits Readout (dead) time: < 30 μs Trigger timing: < 4ns Trigger segment: 0.1 x0.1 to 0.2 x0.2 Implementation: Switched capacitor array for waveform sampling Integrated digitization and trigger circuits Low power consumption: ~100 mw/channel (including FPGA) 3

(Quick) Intro

Short recap Low-energy section: 4 x 23 m tel. (LST) (FOV: 4-5 degrees) energy threshold of some 10 GeV Core-energy array: 23 x 12 m tel. (MST) FOV: 7-8 degrees mcrab sensitivity in the 100 GeV 10 TeV domain High-energy section: 30-70 x 4-6 m tel. (SST) - FOV: ~10 degrees 10 km 2 area at multi-tev energies First Light: ~2016 Completion: ~2019 5

γ-ray enters the atmosphere Electromagnetic cascade

γ-ray enters the atmosphere Electromagnetic cascade ~ 120 m 0.1 km 2 light pool, a few photons per m 2.

γ-ray enters the atmosphere Electromagnetic cascade 10 ns snapshot ~ 120 m 0.1 km 2 light pool, a few photons per m 2.

How to get rid of the night sky background 7

How to get rid of the night sky background 3.2 ms 0 4 10 20 40 100 200 p.e. 7

How to get rid of the night sky background 320 μs 0 4 10 20 40 100 200 p.e. 7

How to get rid of the night sky background 32 μs 0 4 10 20 40 100 200 p.e. 7

How to get rid of the night sky background 3.2 μs 0 4 10 20 40 100 200 p.e. 7

How to get rid of the night sky background 320 ns 0 4 10 20 40 100 200 p.e. 7

How to get rid of the night sky background 32 ns 0 4 10 20 40 100 200 p.e. 7

How to get rid of the proton background 1000x

Dual Mirror Design Secondary optics reduces plate-scale Can use much cheaper photosensors Plus savings in mechanics, electronics 9

Dual Mirror Telescope γ-ray Shower Energy: 1 TeV Impact Distance: 100m Proton Shower Energy: 3.16 TeV Impact Distance: 0m Single Mirror Telescope

Performance enhancement Angular resolution (deg) 40% 12m Single Mirror telescope 9.5m Dual Mirror telescope 11

Implementation: TARGET readout system

TARGET 7 evaluation board FPGA Testing underway at SLAC TARGET 7 Nagoya Wisconsin Preamplifier (1 channel) Leicester Georgia Tech Erlangen Temperature controller, SiPM bias 13

TARGET 5 spec-sheet Specification value Channels 16 Storage cells per channel 16,384 Bandwidth (MHz) ~400 MHz Cross talk @ 3 db frequency ~1% Trigger 4 ea. analog sum of 4 Wilkinson ADCs (ch x samples) 16 x 32 Dead time for 10 bit, 16 ch, 48 samples (48 μs) 10 Sampling frequency (GSa/sec) 0.2-1.4 Effective dynamic range (bits) ~11 14

Sampling frequency tuneable Sampling Frequency Control voltage Tunable between ~0.2 GHz/s and 1.4 GHz/s To maintain phase lock, 64 samples should be a multiple of 8 ns (125 MHz FPGA clock), so sampling frequency should be (8 GSa/sec)/N where N is integer 15

Transfer function Output ADC Input voltage Wide dynamic range ~3000 ADC cnts, corresponds to ~1200 mv. 11.5 bit Small noise ~1.5 ADC counts (~0.6mV corresponds to ~0.5 bits) Resulting in an effective dynamic range of ~11 bits 16

TARGET 7 significant improvement over TARGET 5 TARGET 5 Operating range: 1.2 V Integral nonlinearity: 338 counts TARGET 7 Operating range: 1.9 V Integral nonlinearity: 77 counts 17

The final version: TARGET C and CCTV Moving trigger to small companion ASIC should improve trigger performance Based on studies of T5 with sampling disabled, expect to achieve trigger threshold <4 mv, trigger noise <1 mv TARGET C: production version of TARGET for CTA telescopes, based on TARGET 7 Buffer added to data path to reduce effects of digital activity CCTV: CTA Companion Trigger Variant 16 channels of T5 trigger Includes pre-amp before both data and trigger path (adjustable shaping time ~10 ns, ~40 db gain) with 16 channel output to route to TARGET 5, 7, or C Possible to bypass the internal pre-amp and use external 18

TARGET in CTA cameras

TARGET chips in CTA High channel density enables cameras with low per-channel cost, volume, mass, power consumption (SCT, GCT) TARGET 5 chips and 35 modules produced for GCT (CHEC-M) TARGET 7 chips produced for psct and GCT (CHEC-S) GCT psct 20

TARGET module - 64 channels connection to backplane 30 cm length 5.2 cm square ~200 g without photo- sensor 7 W for 64 channels (not including photo- detector) FPGA 4 TARGET-5 chips MAPMT (swappable for SiPM)

Front-end camera module cost estimates Item 13,000 channels 640,000 channels Unit price Cost/ch Unit price Cost/ch ASIC $65 $4.06 $15 $0.94 FPGA (XC5VLX30T) $235 $3.67 $176 $2.75 HV module $140 $2.19 $105 $1.64 Connectors $1.17 $0.88 FPGA board components $2.42 $1.82 PS board components $1.14 $0.85 PCB fabrications $9~38 $1.70 $5~22 $0.91 Board loading $10~40 $2.44 $8~30 $1.76 Total $18.70 $11.54 Numbers in blue based on real quotes Does not include labor for testing and calibration, or MAPMTs MAPMT cost: $20- $45/ch depending on options (UV glass, super bialkali photocathodes) and quantity (up to 10k MAPMTs for 640k channels)

Functional diagram Preamp TARGET hoto-detectors SiPM bias FPGA L0 trigger x16 Data Peltier control Trigger Slow control Backplane DC/DC 12 V PreAmp/Power board Signal Processing board

GCT Backplane

GCT (aka CHEC) Camera Development line for incorporating TARGET chips into small-size (dual mirror) telescopes In collaboration with colleagues in France, UK, Japan, Netherlands, and Australia

GCT Camera - Concept Pointing LEDs Lid 32 Photosensor modules LED Flasher Units Enclosure ~0.4 m ~45 kg ~450 W Liquid cooling 26

CHEC-M Commissioning Backplane DACQ boards TARGET Modules Preamp Modules MAPMs LED Flashers 27

CHEC-M Commissioning DACQ boards Preamp Modules MAPMs LED Flashers 28

CHEC-M Commissioning Backplane PGA board to generate CLK and Trigger signals DACQ boards TARGET Modules plugged into the backplane and secured with pull-in screws 29

Summary TARGET most cost-eﬀective readout system available in CTA In the process of building prototype cameras based on TARGET-5 (MAPMTs) and TARGET-7 (SiPMTs) Expect to see first light on these cameras (in the lab) in 2015 TARGET C and CCTV (hopefully) final version of TARGET development line 30

TARGET-5 TARGET-7 # of channels 16 16 # of cells/channel 16,384 16,384 Sampling frequency 0.4 1.2 GHz 0.5, 1.0 GHz Bandwidth > 380 MHz > 380 MHz Crosstalk (@ -3dB) < 1% < 1% Dynamic range 0.6 1.0 mv/1.5 V 0.6 1.0 mv/2 V Wilkinson clock speed ~700 MHz ~500 MHz (external, both edges) Digitization time 5.9 µs (12 bit) 8.2 µs (12 bit) # of cells/digitization 32 cells x 16 ch 32 cells x 16 ch Data transfer speed ~90 Mbps x 16 ch ~90 Mbps x 16 ch Dead time (64 cells/ch) 10 bit 2.9 + 8 µs 4.1 + 8 µs 12 bit 11.7 + 8 µs 16.4 + 8 µs # of trigger output Trigger thresh. @ input 4 (4 ch analog sum) + 1 (16 ch analog sum) 25 mv minimum 4 (4 ch analog sum, no gain adjustment) 10 80 mv (2.5 20 p.e. for MST) 0.2 mv step (0.05 p.e. for MST) Trigger threshold noise < 4 mv < 1.6 mv (rms)