ASTRI camera status Giovanni LA ROSA INAF / IASF-Palermo 24-25/02/2012 - CTA SCT 2012 - SLAC

overview of the status of the ASTRI camera project Mechanics and detectors Electronics: FEE and Backplane SiPM test @ OACT Catania

Status of the design (1): mechanics and detectors The ASTRI camera is designed as focal plane instrument of a SCT  CTA-SST. The basic optics parameters are: Equiv Focal Length = 2.15 m F# = 0.5 FOV = 9.6° pixel = 0.17°  6.2x6.2 mm camera Ø = 35cm RoC = 1m A big effort was dedicated to the design of the mechanics of the focal plane. Modularity implies to take care of to the curvature of the focal plane We had to match a curved surface with a certain number of flat modules without loosing the required focusing capability of the optic system. A square module of ~6 cm fits the optics requirement and optimize the numbers of detectors in a single module (16x16 detector units). BUT: we cannot use staircase configuration! Modules must follow the curvature! After this, it was possible to begin the design of the Photon Detector Module (PDM) How to assemble the detectors on top of the PDM

the Detector Unit.. HAMAMATSU S11828-3344M The photon detection system is based on SiPM There are many advantages in using SiPM: excellent single photon resolution, high QE, no HV, no damage when exposed to ambient light. The drawbacks are: the high dark counts (1MHz/mm2), afterpulses, optical crosstalk and Gain strongly dependent on temperature The photon detector is a monolithic multipixel SiPM That can be composed in a bigger module HAMAMATSU S11828-3344M A little border allows the anode signals to be routed on the back side of the detector >dead area Hamamatsu is going to realize a silicon feedthrough 4x4 pixels pixel = 3x3 mm 3600 cells (50x50μ) The cost of the detectors is 200 euro for an order of 500 pieces (496 in ASTRI camera) Hamamatsu said that it could be still lower

from the Detector Unit to the PDM (Photon Detection Module).. pixel dim. = 3x3mm grouping 2x2 physical pixels to obtain 6.2x6.2mm optical pixel = 0.17° PDM = Photon Detection Module 4x4 MPPC = 16x16 pixels (8x8 channels) Dimensions = 56 x 56 mm

this is the way to couple the DUs to the top PCB of the FEE..

coupling the DU PCBs to the top PCB of the PDM

Light guides to recovery the dead area of the borders of the DUs Light collector SiPM detector UNIT (or 4 UNITS) 2.5mm The dead area of the borders of the detector unit can be recovered with a light collector glued on it This is made by glass of high refraction index with a pyramidal shape and tickness of 2.5mm The upper part of the light collector can be coated Simulation of the system (coating + light collector + UV glue) shows a transmission efficiency vs. incidence angle of ~90% (up to 70° incidence angle).

this is the PDM building.. 57 mm LIGHT GUIDES Detector unit (4x4 MPPCs) PCB to I/F MPPC to FEE FEE PCBs 35 mm I/F to the main frame

and this is the way many PDMs compose the focal surface..

the focal surface view: front and lateral Focal Surface is composed by: 37 PDMs (12 half module)  496 SiPMs  1984 optical pixels (0.17°)

and this is the first prototype frame with some PDM mock-up..

model view of the ASTRI camera Estimated weight = 18 Kg (only mechanical structure)

Status of the design (2): electronics Activity on the electronics: The design of a little PCB to host the detector and place it in the upper PDM I/F board The design of the PCB to I/F the detectors to the FEE PCBs The design of the FEE: considering different “sampling memories” and “trigger” (TARGET is our main choice, but.. we are evaluating other sampler ASICs) The study of the design of the back-end electronics is started even if the design of the FEE isn’t still frozen on a definite configuration It was developed a SW for the simulation of the behavior of detector + FEE taking into account even the statistical appearance of afterpulses and optical crosstalk About the interfacing to the external archive and to the control computer, we are defining the data format and the tables of all the parameters that must be monitored (people from Bologna joined the ASTRI project to bring their experience in DAS SW in satellites instruments)

PDM Front End Electronics 64 digitized analog channels Volt STEP-UP 16 ch FPGA PDM SENSORS Control/setting TARGET-2 ? 16 ch Control/setting Control/setting 16 ch 64 digitized analog channels 16 ch Serial link 16 ch TRIGGER LOGIC TRIGGER Control/setting Control/setting

PDM Fornt End Electronics one big critical point: the ASIC TARGET-2 was our first choice.. but what to do now ? - is there any new TARGET chip ready in the very near future? - do we go on with other “sampler” ASICs? (DRS4, ..) - try to explore other ways? “shapers” ASICs (VATA, SPIROC, ..) using TARGET-new depends on how long we have to wait DRS4 is power consuming, 8 ASICs/PDM “shapers” could be interesting: Low power, 2 ASICs/PDM but.. the timing seems to be poor OACT Catania is in charge to explore this choice

PDM Fornt End Electronics Shaper 

Preliminary design ideas for the Back End Electronics BACK END TASKS - Trigger signals routing Clock (GPS) Event Time Tag Store events in a Local Memory Data Packing and Transmission Voltages generation HV / LV distribution I/F to FEE I/F to the external Camera Controller and Data Collection System Operating Modes

ASTRI Back End Electronics Local Memory GPS antenna GPS board CLOCK DATA Ethernet I/F ScienceConsole I/F to DAS FPGA TRIGGER PDMs I/F to Controller Ethernet I/F Camera Controller SET-PROG HKs LVs Power DC line DC/DC converter HV

Status of the design (3): SiPM test @ OACT (Catania) Gain measurements Gain (lab): 7.12 ± 0.14 x 105 @ 31°C - 71.2V Gain (from cal) : 7.50 x 105 @ 25°C – 71.13V

Status of the design (3): SiPM test @ OACT (Catania) Photon Detection Efficiency measurements

some more news in Amsterdam ! Conclusions Mechanical frame fits the required Radius of Curvature PDMs dimensions maintain focusing requirements FEE philosophy under study (depending on the ASIC to be used..) different ASICs are under evaluation Back-End design will start soon simulator helps in the evaluation of different HW configurations OACT Catania lab will continue to run other characterization tests on the Hamamatsu detectors some more news in Amsterdam ! 10 people are working on the camera: 5 in Palermo + 5 in Catania contact us: eteam.astri@ifc.inaf.it