SiPMs are fast silicon-based pixelated photo-diodes with intrinsic amplification and spectral sensitivity from the optical to the soft X ray domain. The rather new technology – first devices became commercially available only in 2007 – quickly attracted a broad range of applications, from astrophysics, particle and nuclear physics to medical imaging and homeland security. More and more they replace the conventional photo-multipliers in scintillation detectors now being constructed or conceived for high energy or heavy ion experiments. The demand for smaller pixels, higher sensitive area fill factors, larger surfaces and lower noise is driving the development pursued by partners in industry, and in the Max Planck society. Modern 3D interconnection technologies could be used to integrate the sensors with their readout electronics and thus open up further potential applications, e.g. as track detectors or beam monitors.
Goals and Activities
In the framework of the technology platform the complementary expertise and infrastructure at DESY, FZJ, GSI, HZB and HZDR will be better connected, further developed and enhanced with new installations. The idea is to benefit from current developments in fine-pitch 3D interconnection and integration technology. As a concrete step, digital SiPM will be developed, sensors or arrays where individual pixels are directly coupled to digital read-out chips. This brings spatial information, single pixel noise suppression, fast signal processing and low power consumption. In principle the technological ingredients are at hand, but the industrial standard for interconnect separation is an order of magnitude too large and necessitates dedicated development. Initially, one can start with bump bonding techniques developed for LHC pixel detectors, later also lithographic methods can be used.
Eventually, the developments shall result in a photo-sensor, operated in Geiger mode at high intrinsic amplification (ca. 106), an active area of a few mm2, sub-divided into 20 μm pixels, each with independent digital read-out. This would be suitable for the read-out of segmented scintillation detectors. The time resolution should be better than 100 ps to meet the requirements of time-of-flight and Cerenkov ring detectors. The sensor shall be integrated with its read-out chip using 3D technology and have a geometry that allow seamless stitching for the realisation of larger arrays for synchrotron radiation applications.
The sensor, the interconnection technology and the read-out electronics can be developed in parallel and tested independently. The first sensor and chip prototypes are foreseen to have larger pixels, such that they can be inter-connected using the standard processes of semiconductor industries.
|DESY||sensor development (in cooperation with MPI Munich), component tests, interconnection processes (with industrial partners). The required infratstructure will be created in the framework of the first column of this portfolio|
|FZJ||study of applications in high magnetic fields, such as in medical diagnostics (using existing installations)|
|GSI||fast signal processing near the front-end for nuclear physics detectors, study of temperature sensitivity and radiation hardness (existing test beds)|
|HZB||development of a UV-compatible detector system based on the new sensors, test stand (with HZDR) for the characterisation using the Helmholtz sources for ultra-fast X ray pulses (at HZB, DESY, HZDR)|
|HZDR||characterisation of ultra-fast timing properties in a brad spectral range, us of short electron accelerator pulses, use of the semiconductor lab and cooperation with industrial partners|
The task sharing altogether reflects the existing infrastructure and expertise. The portfolio funds enable all centres to sustainably enhance it and benefit from innovative 3D technologies and optimise it for their own research projects.
Max-Planck-Institute for Physics, Munich, Univerties Aachen, Heidelberg, Wuppertal, Hamburg.