Mechanical design for SiPM based 64 pixels Camera prototype A. P. K. Kutty, P. Verma, S. S. Upadhya, B. B. Singh, S. R. Patel, N. K. Parmar, V. R. Chitnis, K. S. Gothe

Tata Institute of Fundamental Research, Colaba, Mumbai 400005

Camera prototype

256 pixel Camera specification

Telescope TACTIC vertex

Size of mirror dish 4m dia

Pixel Sensor 13x13mm SiPM

LC entry size 22.1x22.1 mm2

Field of View 5ox5o

Pixel resolution 0.3o

Aperture area 360x360 mm2

Camera Dimension 500x500x1500mm

Weight ~100Kg

Operating temperature -20oC to 40oC

NSB filter Dichroic glass

Cooling Forced air cooling

Cherenkov Telescope

(Mirror dish dia of 4m)

Introduction: SiPM based 256 pixel Camera is being developed in TIFR for a 4m class Atmospheric Cherenkov Telescope to be finally deployed at Hanle (4300m altitude), Ladak. The Camera is planned with a modular structure with 256 pixels organized into 16 modules of 16 pixels each in the front-end as well as in the back-end of the camera. The Camera has an aperture of 5ox5o with a pixel resolution 0.3o. The prototype of 64 pixels is under development.

Camera

PCM housing specification

Size (mm) 90 x 90 x 320 ht.

Weight 2 kg

Geometric Area 201 mm2

Maximum allowed area loss due to

structural requirement

< 10%

Parallelism requirement between

lateral surfaces

<0.2 mm

Flatness requirement < 0.2 mm over 400 mm

Structure material ABS plastic

Merits & Impacts: 1.Minimum dead area in the camera

aperture 2.Sensors & Front-end electronics within the

same structure 3.Easy and precise alignment of Light

Concentrators and SiPMs 4.Efficient handling due to stand-alone

system concept 5.Ease in fabrication & testing

Assembled PCM

LC

AMP cards-4nos

LV card

Bias card 1

Light Concentrator: Light Concentrator(LC) is a reflector with square entry and square exit to converge light from larger area pixel aperture onto smaller area SiPM. An LC assembly is made by gluing the 16 LCs on a machined Aluminium base. The LC assembly is mounted on a PCM housing so that every LC exit is aligned to a SiPM sensor.

LC before coating

LC assembly

LC internal geometry

LC module

The LC module is having a square entry and exit of 21.1 mm & 12.4 mm respectively, connected with a parabolic curve. The height of the module is 23.06 mm. Thickness of LC at entry is 0.5 mm which minimizes dead space between pixels. LC is made up of ABS plastic by vacuum casting method. The halves of LC are vacuum deposited with aluminium to make it as reflectors. Distribution of LC Efficiency

LC cluster

Bias card 2

64 pixel Prototype status

Conclusion: The realization of proto-type provided the necessary information and helped to study the feasibility of critical design aspects and manufacturing process for the completion of 256 pixel SiPM based camera for future mission.

Interface plate Front End

Back End 64 pixel prototype structure

M2.5 inserts for PCB mtg.

Pixel Cluster Module (PCM) housing: The Pixel cluster module (PCM) houses all the front-end electronics cards, SiPMs, LC assembly catering to a cluster of 16 pixels. The PCM housing is designed for easy assembly of front -end electronics cards with a consideration to efficient heat dissipation, extreme temperatures at high altitude site and easy servicing. The PCM housing is a single shell made of ABS plastic using 3D printing for master mould and vacuum casting process for the production.

Acknowledgement: We thank Mr. Santhosh S Chavan for the immense contributions towards realizing the prototype camera.

Email: kutty@tifr.res.in Tel: 022-22782135