The European Photon Imaging Camera (EPIC) consortium has provided the focal plane instruments for the three X-ray mirror systems on XMM-Newton. Two cameras with a reflecting grating spectrometer in the optical path are equipped with MOS type CCDs as focal plane detectors (Turner 2001), the telescope with the full photon flux operates the novel pn-CCD as an imaging X-ray spectrometer. The pn-CCD camera system was developed under the leadership of the Max-Planck-Institut fur extraterrestrische Physik (MPE), Garching. The concept of the pn-CCD is described as well as the dierent operational modes of the camera system. The electrical, mechanical and thermal design of the focal plane and camera is briefly treated. The in-orbit performance is described in terms of energy resolution, quantum eciency, time resolution, long term stability and charged particle background. Special emphasis is given to the radiation hardening of the devices and the measured and expected degradation due to radiation damage of ionizing particles in the rst 9 months of in orbit operation.

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The European Photon Imaging Camera on XMM-Newton: The pn-CCD camera

Fourth generation accelerator-based light sources, such as VUV and X-ray Free Electron Lasers (FEL), deliver ultra-brilliant (∼1012–1013 photons per bunch) coherent radiation in femtosecond (∼10–100 fs) pulses and, thus, require novel focal plane instrumentation in order to fully exploit their unique capabilities. As an additional challenge for detection devices, existing (FLASH, Hamburg) and future FELs (LCLS, Menlo Park; SCSS, Hyogo and the European XFEL, Hamburg) cover a broad range of photon energies from the EUV to the X-ray regime with significantly different bandwidths and pulse structures reaching up to MHz micro-bunch repetition rates. Moreover, hundreds up to trillions of fragment particles, ions, electrons or scattered photons can emerge when a single light flash impinges on matter with intensities up to 1022 W/cm2. In order to meet these challenges, the Max Planck Advanced Study Group (ASG) within the Center for Free Electron Laser Science (CFEL) has designed the CFEL-ASG MultiPurpose (CAMP) chamber. It is equipped with specially developed photon and charged particle detection devices dedicated to cover large solid-angles. A variety of different targets are supported, such as atomic, (aligned) molecular and cluster jets, particle injectors for bio-samples or fixed target arrangements. CAMP houses 4π solid-angle ion and electron momentum imaging spectrometers (“reaction microscope”, REMI, or “velocity map imaging”, VMI) in a unique combination with novel, large-area, broadband (50 eV–25 keV), high-dynamic-range, single-photon-counting and imaging X-ray detectors based on the pnCCDs. This instrumentation allows a new class of coherent diffraction experiments in which both electron and ion emission from the target may be simultaneously monitored. This permits the investigation of dynamic processes in this new regime of ultra-intense, high-energy radiation—matter interaction. After an introduction into the salient features of the CAMP chamber and the properties of the redesigned REMI/VMI spectrometers, the new 1024×1024 pixel format pnCCD imaging detector system will be described in detail. Results of tests of four smaller format (256×512) devices of identical performance, conducted at FLASH and BESSY, will be presented and the concept as well as the anticipated properties of the full, large-scale system will be elucidated. The data obtained at both radiation sources illustrate the unprecedented performance of the X-ray detectors, which have a voxel size of 75×75×450 μm3 and a typical read-out noise of 2.5 electrons (rms) at an operating temperature of −50 °C.

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Large-format, high-speed, X-ray pnCCDs combined with electron and ion imaging spectrometers in a multipurpose chamber for experiments at 4th generation light sources

Charge-coupled device (CCD) area x-ray detector technology is reviewed. CCD detectors consist of a serial chain of signal components, such as phosphors, fiber optics or lenses, image intensifiers and the CCD which serve to convert the x-ray energy to light or electron-hole pairs and to record the spatially resolved image. The various combinations of components that have been used to make CCD detectors are described and the properties of each of the critical components are discussed. Calibration and correction procedures required for accurate data collection are described. The review closes with a brief description of future directions for solid-state area x-ray detectors.

Charge-coupled device area x-ray detectors

A new pn-CCD with an activa area of 3 × 1 cm2 was recently fabricated for ESA's X-ray Multi Mirror Mission (XMM). The front-end electronics has been integrated on the same chip as the detector, and its noise behaviour was investigated. X-rays from a 55Fe source have been used for the absolute calibration. The measured electronic Equivalent Noise Charge (ENC) of the on-chip amplifier was 8.8 e− at room temperature and 2.2 e− at the CCD operating temperature of 150 K. The improvements with respect to the last version with noise figures of 4.8 e− (at 150 K) are due to the reduction of the total input capacitance by a factor of 1.6, the improvement of the transistor transconductance by a factor of 2, and the reduction of 1 ƒ noise because of the different p-well implant with a better thermal annealing.

The pn-CCD on-chip electronics

The CERN Axion Solar Telescope (CAST) has been in operation and taking data since 2003. The main objective of the CAST experiment is to search for a hypothetical pseudoscalar boson, the axion, which might be produced in the core of the sun. The basic physics process CAST is based on is the time inverted Primakoff effect, by which an axion can be converted into a detectable photon in an external electromagnetic field. The resulting x-ray photons are expected to be thermally distributed between 1 and 7 keV. The most sensitive detector system of CAST is a pn-CCD detector combined with a Wolter I type x-ray mirror system. With the x-ray telescope of CAST a background reduction of more than 2 orders of magnitude is achieved, such that for the first time the axion photon coupling constant gaγγ can be probed beyond the best astrophysical constraints gaγγ < 1 × 10−10 GeV−1.

https://iopscience.iop.org/article/10.1088/1367-2630/9/6/169/pdf

The x-ray telescope of CAST

A new detector-amplification principle proposed by Kemmer and Lutz in 1986 has been experimentally verified. Outstanding features of this device are the built-in amplification, the signal charge storage capability and the possibility of repeated non-destructive readout. The device was used for detection of X-rays from a 241 Am and from Am and from an 55 Fe source. Very low noise figures ( σ =30 electrons corresponding to an energy resolution of FWHM = 250 eV at 6 keV energy) have been obtained at room temperature. Various applications of the structure either as detector or as purely electronic element are possible. One of the most intriguing is the use as a pixel detector with random access non-destructive readout. This device may be operated at very low power, as only reading (of one single pixel at a time), not storing, consumes power. Further options of the device are fast clearing, gating and variation of the pixel size during readout. The latter property can be used to drastically increase the readout speed compared to more standard two dimensional devices as e.g. CCD detectors, as one may restrict the high density readout to regions of interest determined beforehand by a coarse scan of the whole detector. An alternative use of the device is as an analog or digital memory, or as a simple transistor with drastically reduced parasitic capacitances. Possible further developments are the combination with a novel three dimensional analog storage device which may either be used as a detector with built-in storage of several charge images or as a three dimensional analog memory.

Experimental confirmation of a new semiconductor detector principle

MAXI (MPI/AIT X-ray Imager) is part of a proposal submitted to the European Space Agency (ESA) as focal plane instrumentation of the X-ray Multi Mirror Mission (XMM). Within a collaboration of 13 European institutes we have proposed a fully depleted (sensitive) pn CCD of 280 μm thickness with a homogeneous sensitive area of 36 cm2 and a pixel size of 150×150 μm2 which is well matched with the telescope's angular resolution of 30 arcsec translating to a position resolution of approximately 1 mm in the focal plane. 
 
The X-ray sensitivity will be higher than 90% from 250 eV up to 10 keV, the readout time in the full frame mode of the complete focal plane will be 2 ms with a readout noise of better than 5 e− (rms). Prototypes of all individual components of the camera system have been fabricated and tested. The camera concept will be presented. The measured transfer properties of the CCD and the on-chip electronics will be treated. Taking into account the coupling of the on-chip amplifier to the following front-end electronics the expected performance will be derived.

The MPI/AIT X ray Imager (MAXI): High speed PN-CCD's for x ray detection

MAXI (MPI/AIT X-ray Imager) is part of a proposal submitted to the European Space Agency (ESA) as focal plane instrumentation of the X-ray Multi Mirror Mission (XMM). Within a collaboration of 13 European institutes we have proposed a fully depleted (sensitive) pn CCD of 280 μm thickness with a homogeneous sensitive area of 36 cm2 and a pixel size of 150×150 μm2 which is well matched with the telescope's angular resolution of 30 arcsec translating to a position resolution of approximately 1 mm in the focal plane. The X-ray sensitivity will be higher than 90% from 250 eV up to 10 keV, the readout time in the full frame mode of the complete focal plane will be 2 ms with a readout noise of better than 5 e− (rms). Prototypes of all individual components of the camera system have been fabricated and tested. The camera concept will be presented. The measured transfer properties of the CCD and the on-chip electronics will be treated. Taking into account the coupling of the on-chip amplifier to the following front-end electronics the expected performance will be derived.

The MPI/AIT X-ray imager (MAXI) — High speed pn CCDs for X-ray detection

The authors have fabricated 280- mu m-thick fully depletable p-n charge -coupled devices (CCDs) on high-resistivity silicon ( approximately 2.5 k Omega -cm). Their operation is based on the semiconductor drift-chamber principle. They are designed as energy- and position-sensitive radiation detectors for (minimum) ionizing particles and X-ray imaging. Two-dimensional semiconductor device modeling demonstrates the basic charge-transfer mechanisms. Prototypes of the detectors have been tested in static and dynamic conditions. A preliminary charge-transfer inefficiency was determined 6*10/sup -3/. The charge loss during the transfer is discussed, and an improved design, which is now being produced, is presented. >

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First tests with fully depleted pn-CCD's

Fully depletable pn CCD's on high resistivity 280 pm thick silicon (e e:-, 2.5 kIlcm) have been fabricated. Their operation is based on the semiconductor drift chamber principle proposed by Gatti and Rehak. They are designed as energy and position sensitive radiation detectors for X-rays and (minimum-) ionizing particles. Two-dimensional semiconductor device modeling demonstrates the basic charge transfer mechanisms. Prototypes of the detectors have been tested in quasistatic and dynamic conditions. A preliminary charge transfer inefficiency e, has been determined to less than 10-3 at shift frequencies varying between 500 kHz and 6 MHz. The charge loss during the transfer is discussed. As a consequence, an improved design had been developed for a new fabrication iteration which is currently being tested.

M. Sterzik

Papers

Experimental confirmation of a new semiconductor detector principle

The MPI/AIT X ray Imager (MAXI): High speed PN-CCD's for x ray detection

The MPI/AIT X-ray imager (MAXI) — High speed pn CCDs for X-ray detection

First tests with fully depleted pn-CCD's

Development And Test Of Fully Depleted Pn-CCD's For X-Ray Detection