Development of Planacon Tubes with Cross Strip Readouts and Atomic Layer MCPs

Microchannel plate (MCP) detectors have been used on many ultraviolet (UV) space based observatories. Future NASA missions would benefit from scaled designs with larger areas, higher spatial resolution, and high counting rate capability. These prospects are being successfully demonstrated with cross strip (XS) anode readouts, but the electronics that read out such detectors would require reduction in size, weight, and power. The GRAPH ASIC was developed as an efficient high bandwidth solution to read out cross strip anodes for MCP detectors. First generation GRAPH ASICs have been wire bonded to circuit boards and initial testing and characterization have been done. Firmware and software have been implemented to process XS anode events producing X-Y photon positions. To further test and characterize performance of the GRAPH ASIC a GRAPH board is being used to read out photon events from an MCP detector with a cross strip anode. We present preliminary results on GRAPH design and operation. In addition we demonstrate photon detection with position and pulse height analysis and a description of the firmware currently being used to carry out these tests.

Microchannel plate based detectors are widely used for photon counting spectroscopy and imaging in astronomical, high energy physics and remote sensing applications^1-15. We present progress in the development of imaging cross strip readout detectors using novel microchannel plates functionalized by atomic layer deposition (ALD). ALD microchannel plates have established formats of 10 cm with 10 μm pore sizes and 20 cm with 20 μm pores. ALD MCPs show with high quantum efficiency (>50% @115 nm) using opaque alkali halide photocathodes and very low background levels (0.05 events cm^-2) have been achieved. Readout systems have also evolved and now cross-strip anodes and encoding electronics enable high spatial resolution (<20 μm) at low gain (10⁶) and over large formats (10 cm) with high dynamic range (>5 MHz). These characteristics are essential for UV instrument concepts currently under study for NASA including the Large UV/Optical/IR Surveyor (LUVOIR)¹⁶, the Habitable Exoplanet Imaging Mission (HABEX)¹⁶, and Cosmic Evolution Through UV Spectroscopy (CETUS)¹⁶.

Advances in photocathodes (GaN, Diamond, GaAs), microchannel plates (Silicon MCP's), and readouts (Cross strip) are poised to make a significant impact on the capabilities of future space instruments. Alkali halide cathode efficiencies have been improved and GaN photocathodes have achieved >30% DQE in the UV with a bandpass limit of ~400nm. In addition diamond photocathodes have been made with 40% DQE and bandpass up to 200nm, and GaAs photocathodes with ~50% DQE in the visible have been made. This offers the potential for efficient photon counting from 10 - 900nm. Silicon MCP's of 25mm format with ~7μm pores, have been made, achieving gain of nearly 104 for a single Si MCP. The quantum detection efficiency for Si MCP's is the same as glass MCP's, but the background is as low as ~ 0.02 events sec-1 cm-2, the best for any MCP. Flat fields are free of any periodic modulation, and the gain uniformity is good. Silicon MCP's have low stopping power for X, gamma and cosmic rays, are stable at high temperatures (>800°C), and chemically compatible with many photocathodes. The cross delay line and cross strip anodes are based on multi-layer metal and ceramic cross strip patterns. Event positions are encoded by the difference of signal arrival times at the anode contacts (delay line) or by direct sensing of the charge on each strip (cross strip) and determination of the charge cloud centroid for each event. The spatial resolution (<5μm) achieved is sufficient to resolve 7μm microchannel plate pores while using low MCP gain (≈2 x 106). Image linearity is good enough to see distortions in the microchannel plate pore alignment, and the low MCP gain will enhance the overall lifetime of MCP detector systems.

We have implemented cross strip readout microchannel plate detectors in 18 mm active area format including open face (UV/particle) and sealed tube (optical) configurations. These have been tested with a field programmable gate array based parallel channel electronics for event encoding which can process high input event rates (> 5 MHz) with high spatial resolution. Using small pore MCPs (6 μm) operated in a pair, we achieve gains of >5 x 10 5 which is sufficient to provide spatial resolution of <35 μm FHWM, with self triggered event timing accuracy of ~2 ns for sealed tube optical sensors. A peak quantum efficiency of ~19% at 500 nm has been achieved with SuperGenII photocathodes that have response over the 400 nm to 900 nm range. Local area counting rates of up to >200 events/mcp pore sec -1 have been attained, along with image linearity and stability to better than 50 μm.

Improved efficiency of high resolution thermal and cold neutron imaging

과학위성 1호의 주탑재체인 원자외선 분광기의 검출기 전자부에 대한 특성을 분석하였다. FIMS (Far-ultraviolet Imaging Spectrograph)는 교차 지연선 양극을 가진 MCP(micro-channel plate)를 사용하여 입사된 원자외선 광자의 위치를 검출한다. MCP에 입사하는 광자는 MCP을 통해 전자형태로 변환되고 증폭된다. 증폭된 전하운의 중심은 양분되어 연결된 지연선을 통해 양단으로 나가게 되고, 지연선의 양단에서 전하운의 도착시간 차이를 구하여 입사된 광자의 위치를 판독한다. FIMS의 경우 2개의 MCP 검출기를 갖고 있으며, 각각 25mm<TEX>$\times$</TEX>25mm의 유효 크기를 갖고있다. 또 신호처리계는 1채널의 신호처리 회로계를 통해 2개의 검출기에 대한 영상검출이 가능하도록 함으로써 신호처리계의 복잡성을 피하고 아울러 전력과 무게 비용을 줄였다. 이 시스템을 통해 높은 시간 및 공간 분해능(<<TEX>$35{\times}75$</TEX>ps FWHM)을 얻었으며, 6W 이하의 저전력 시스템을 구현하였다. We describe some performance of the detector electronics system for the FIMS (Far-ultraviolet Imaging Spectrograph) mission. The FIMS mission to map the far ultraviolet sky uses MCP (micro-channel plate) detectors with a crossed delay line anode to record photon arrival events. FIMS has two MCP detectors, each with a ~25mm<TEX>$\times$</TEX>25mm active area. The unconventional anode design allows for the use of a single set of position encoding electronics for both detector fields. The centroid position of the charge cloud, generated by the photon-stimulated MCP, is determined by measuring the arrival times at both ends of the anode following amplification and external delay. The temporal response of the detector electronics system determines the readout's positional resolution for the charge centroid. High temporal resolution (<<TEX>$35{\times}75$</TEX>ps FWHM) and low power consumption (< 6W) were achieved for the FIMS detector electronics system.

NASA has funded, through their Strategic Astrophysics Technology (SAT) program, the development of a cross strip (XS) microchannel plate (MCP) detector with the intention to increase its technology readiness level (TRL), enabling prototyping for future NASA missions. One aspect of the development is to convert the large and high powered laboratory Parallel Cross Strip (PXS) readout electronics into application specific integrated circuits (ASICs) to decrease their mass, volume, and power consumption (all limited resources in space) and to make them more robust to the environments of rocket launch and space. The redesign also foresees to increase the overall readout event rate, and decrease the noise contribution of the readout system. This work presents the design and verification of the first stage for the new readout system, the 16 channel charge sensitive amplifier ASIC, called the CSAv3. The single channel amplifier is composed of a charge sensitive amplifier (pre-amplifier), a pole zero cancellation circuit and a shaping amplifier. An additional output stage buffer allows polarity selection of the output analog signal. The operation of the amplifier is programmable via serial bus. It provides an equivalent noise charge (ENC) of around 600 e^− and a baseline gain of 10 mV/fC. The full scale pulse shaped output signal is confined within 100 ns, without long recovery tails, enabling up to 10 MHz periodic event rates without signal pile up. This ASIC was designed and fabricated in 130 nm, TSMC CMOS 1.2 V technology. In addition, we briefly discuss the construction of the readout system and plans for the future work.

We describe the design and report on the experimental results of a novel thermal and cold neutron imaging detector utilizing neutron sensitive (10B-doped) microchannel plates (MCPs). In this detector, the incoming neutron interaction products produce secondary electrons at the pores adjacent to the absorption point within the MCP glass. This electron signal is then multiplied by a stack of conventional MCPs within those adjacent pores limiting the spread of the signal to less than two pore diameters (currently 6-10 mum pores on 8-12 mum centers). The event position then can be encoded by a number of readout techniques already developed for photon/charged particle counting applications. This paper presents the results of experimental evaluation of neutron sensing MCP detector with Medipix2 readout allowing operation at high counting rate mode (>100 MHz level) at a spatial resolution limited by the 55 mum pixel size of the Medipix2 readout. Other attractive features of MCP neutron detectors are their high detection efficiency (approaching 50% levels) for thermal and cold neutrons and the absence of readout noise.

Microchannel plate (MCP) is an important compact two-dimension multiplier for parallel multiplication of charged particles. With the advantages of high temporal resolution, high spatial resolution, high electron gain and compact structure, microchannel plate has become an important potential readout device for cryogenic quantum computing, such as the quantum computation based on floating electrons of liquid helium surface. For the sake of ultra-fast reading, it requires the signal readout time is less than 10^-5 s at a temperature lower than 30K in the cryogenic quantum computing. However, the bulk resistance of MCP multiplier became giant at cryogenic temperature for the property of huge negative temperature coefficient of resistance, almost 10⁵ Gohm at 20K~30K, resulting in a readout time of 10^-2 -1s at cryogenic temperature, which was one of the major bottlenecks for the application of MCPs in the cryogenic quantum computing. In this paper, the bulk resistance of MCPs in two different bismuth contents (1at%, 2.4at%) under the same hydrogen reduction temperatures (730K) were present as the surrounding temperature controlled from 300K to 20K. The cryogenic bulk resistance of MCP was only decreased into 24% with the increase bismuth content from 1at% to 2.4at%, while thereof the normal bulk resistance was decline into 5%. The normal bulk resistance reduced only in the manner of improving the conductivity of conductive layer, could also increase the temperature-resistance sensitivity of MCP, leading an even greater temperature coefficient of resistance, which deteriorated the stability of readout in the cryogenic quantum computing.

The design of a new high-transparency device based on a Micro Channel Plate (MCP) detector was recently proposed for monitoring the flux and beam spatial profile of neutron beams. The proposed device consists of a very thin aluminum (Al) foil (with a [Formula: see text]Li deposit) placed in the neutron beam and an MCP detector equipped with a phosphor-screen readout linked to a charge-coupled device (CCD) camera outside the neutron beam. A critical feature of this device is that it uses an electrostatic mirror to minimize the perturbation of the neutron beam (i.e., absorption and scattering). It can be used at existing neutron time-of-flight (n_TOF) facilities (in particular at the n_TOF facility at CERN) for monitoring the flux and spatial profile of neutron beams in the thermal and epithermal region. The experimental tests conducted for this study using a radioactive source to determine the behavior of the electrostatic mirror behavior will be presented and discussed in this paper.

Neutron Imager and Flux Monitor Based on Micro Channel Plates (MCP) in Electrostatic Mirror Configuration

High-resolution UV, alpha and neutron imaging with the Timepix CMOS readout

Experimental study of spatial resolution of MCPs for compact high-resolution neutron radiography system

ALD-GCA-MCPs are a technology advancement that affords microchannel plates (MCPs) with significant performance benefits compared to conventional MCP technology. Incom now routinely produces ALD-GCA-MCPs with dimensions up to 20 cm x 20 cm. Notable advancements and benefits over conventional lead-oxide based MCPs are larger size and higher mechanical stability, high and stable gain (>1e4for single MCP @ 1000 V, stable gain to ≥ 1 C/cm2 extracted charge), low dark counts (≤ 0.05 cts/sec/cm2), ~3x lower gamma-ray sensitivity, and the unique ability to individually customize and control the MCP resistance and secondary electron emission (SEE) amplification characteristics. ALD-GCA-MCPs find application in a variety of photon and charged particle counting applications and are particularly suited for applications that require fast timing, high spatial resolution, radiation hardness, and long detector life times, such as Ion-TOF, electron spectroscopies, and a variety of other analytical instruments. They can also be incorporated into low-power, low-background photodetectors suitable for applications in extreme environments such as remote sensing applications in rugged environments, in space flight instrumentation, as well as in high-energy physics and nuclear physics experiments. In this paper we will provide a brief ALD-GCA-MCP technology overview highlighting recent developments that focused on improving the glass capillary array (GCA) substrate, and their implications for large-area photodetectors and spectrometers used in nuclear and high energy physics, space science, and other sensing applications.

The Far Ultraviolet Spectroscopic Explorer (FUSE) satellite was launched into orbit on June 24, 1999. FUSE is designed to make high resolution ((lambda) /(Delta) (lambda) equals 20,000 - 25,000) observations of solar system, galactic, and extragalactic targets in the far ultraviolet wavelength region (905 - 1187 Angstrom). Its high effective area, low background and planned three year life allow observations of objects which have been too faint for previous high resolution instruments in this wavelength range. The FUSE instrument includes two large format microchannel plate detectors. Each detector system consists of two microchannel plate segments in a Z-stack configuration with double delay line anodes and associated electronics. High detector spatial resolution was required in order to obtain scientific data with high spectral resolving power, and low detector background was necessary in order to observe faint objects. We describe the performance of the FUSE detectors during their first year on orbit, including the mechanical and thermal stability, throughput, background, and flat field of the detector system. We will also discuss the regular single event upsets of the detector electronics, and the strategy adopted in order to minimize their impact on mission efficiency.