Coherent X-ray diffraction experiments on synchrotron X-ray beamlines require detectors with high spatial resolution and large detection area. The read-out chip developed by the MEDIPIX3 collaboration offers a small pixel size of 55 microns resulting in a very high spatial resolution when coupled to a direct X-ray conversion segmented silicon sensor. MEDIPIX3 assemblies present also the advantages of hybrid pixel detectors working in single photon counting mode: noiseless imaging, large dynamic range, extremely high frame rate. The EXCALIBUR detector is under development for the X-ray Coherence and Imaging Beamline I13 of the Diamond Light Source. This new detector consists of three modules, each with 16 MEDIPIX3 chips which can be read-out at 100 frames per second in continuous mode or 1000 frames per second in burst mode. In each module, the sensor is a large single silicon die covering 2 rows of 8 individual MEDIPIX3 read-out chips and provides a continuous active detection region within a module. Each module includes 1 million solder bumps connecting the 55 microns pixels of the silicon sensor to the 55 microns pixels of the 16 MEDIPIX3 read-out chips. The detection area of the 3-module EXCALIBUR detector is 115 mm × 100 mm with a small 6.8 mm wide inactive region between modules. Each detector module is connected to 2 FPGA read-out boards via a flexi-rigid circuit to allow a fully parallel read-out of the 16 MEDIPIX3 chips. The 6 FPGA read-out boards used in the EXCALIBUR detector are interfaced to 6 computing nodes via 10Gbit/s fibre-optic links to maintain the very high frame-rate capability. The standard suite of EPICS control software is used to operate the detector and to integrate it with the Diamond Light Source beamline software environment. This article describes the design, fabrication and characterisation of the MEDIPIX3-based modules composing the EXCALIBUR detector.
A major problem of usual current measurement setup is the severe limitations on the bandwidth due to room temperature electronics. This restricts the practical measurement rate to below 10 Hz and makes impossible to observe the evolution of a quantum state in real time. Here we describe a measurement on a silicon single electron transistor (SET) carried out using a custom CMOS measurement circuit in close proximity to the device under test. Both the device and the CMOS circuit are maintained in the same cryogenic environment. Quantum mechanical states in the single electron transistor (SET) were mapped by continuous microwave spectroscopy. The real time evolution of a particularly long lived quantum mechanical state was observed in a single shot measurement, made possible by the much faster measurement rate. This technique will shortly be applied to the measurement of coherent states in a charge qubit device made of a silicon double dot.
We have fabricated a custom cryogenic complementary metal-oxide-semiconductor integrated circuit that has a higher measurement bandwidth compared to conventional room temperature electronics. This allowed implementing single shot operations and observe the real-time evolution of the current of a phosphorus-doped silicon single electron transistor that was irradiated with a microwave pulse. Relaxation times up to 90μs are observed, suggesting the presence of well isolated electron excitations within the device. It is expected that these are associated with long decoherence time and the device may be suitable for quantum information processing.
We present the development and prototype test of the LPD instrument, a novel pixel detector for the European XFEL. At XFEL the LPD detector must be capable of operating with a frame rate of 4.5MHz and record images with a dynamic range of 1:100,000 photons (12keV) whilst maintaining low noise. The prototype LPD system has a large in pixel memory depth of 512 images that can be selected with a flexible veto system. Data is then transferred off the detector head in between XFEL pulses with an accompanying high rate data acquisition system. The system has been prototyped and assembled into an LPD detector head that contains custom silicon sensors and ASICs as well as a programmable data acquisition cards and supporting electronics and mechanics. A second version of the ASIC has also been submitted for manufacture. The experiences with our first prototype are presented.
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