使用曲面微通道板和感应电荷位置灵敏阳极的软X射线-极紫外光子计数成像探测器研究

An analysis of microchannel plate composition and its effect on extreme ultraviolet quantum efficiency

The EUV grating spectrograph (EGS) as part of the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) solar EUV experiment (SEE) presents a number of performance challenges for its microchannel plate (MCP)- based detector. The EGS measures the solar spectral irradiance from 25 to 200 nm. The intensities of the line and continuum emissions over this spectral range vary by up to five orders of magnitude. While a variety of transmission filters are strategically used to bring the signal over the entire spectrum into the dynamic range of a single chevron pair of MCPs, a number of concerns regarding the characteristic behavior of MCPs remain. The nominal TIMED mission is two years while the extended mission potentially doubles to four years. Over this period, the MCP response is expected to change to some extent. Detailed changes in MCP performance are notoriously application dependent,however. In order to better anticipate and accommodate these changes over the duration of the mission as well as to potentially enhance detector performance, we are performing a series of life-tests on a variety of MCPs. In these tests we characterize MCP gain, pulse height distribution, quantum detection efficiency, and linearity as function of accumulated charge and exposure to atmosphere. Here we report on the result of these test.s

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.

The quantum detection efficiency of photon-counting microchannel-plate detector channels can be increased by a factor of 2 in the extreme ultraviolet bandpass, from 256 A to 1024 A, by subjecting the input channel plate to a chemical solution treatment. The efficiency increase has proven to be insensitive to the exposure of laboratory atmosphere and is stable over the extracted charge lifetime equivalent of multiyear astrophysical observations. Chemically treated microchannel plates that are overcoated with opaque photocathodes of KBr and CsI show a factor of 2 quantum detection efficiency increase from 834 A to 1100 A in comparison with previous measurements using conventional untreated microchannel plates.

We present investigations on the improvements in quantum detection efficiency (QDE) of microchannel plate (MCP) detectors resulting from the application of various photocathode materials. Nine different photocathode materials were deposited and their QDE measured in the soft x-ray and UV region from 12 angstrom to 1850 angstrom. Four of these materials (CsCl, RbCl, RbI, BaCl) significantly enhance the QDE performance of bare MCPs, and five materials were proven unsatisfactory (AgCl, LiCl, LiI, LiF, MgBr). CsCl has very high (greater than 90%) short wavelength QDE and both CsCl and RbI have UV QDE in the region of 40%. Our studies also include life testing of a KBr photocathode for a period of over 5 years. This shows good stability, and the angular response and photoemissive characteristics over time are described. The effects of long wavelength QDE activation of KBr by exposure to 2537 angstrom photons are discussed.

The present article summarizes the results of two experiments which were performed to study the radiation properties of backward transition radiation (BTR) in the extreme ultraviolet (EUV) region. This wavelength region is of particular interest for transverse beam profile imaging, because the spatial resolution is improved as a result of the reduced contribution in the imaging process of the fundamental diffraction limit. In addition, the influence of coherent effects in the transition radiation emission process, which have been observed in the visible region, might be mitigated. The first experiment, dedicated to the investigation of the BTR angular characteristics, indicates that the radiation yield in the EUV region is higher than theoretically expected and that it is even comparable to the yield in the visible region. The second measurement was devoted to transverse beam profile imaging based on quasimonochromatic BTR, in both the EUV and the visible region, and is a proof-of-principle experiment demonstrating that EUV BTR is a suitable candidate for standard beam profile diagnostics.

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.

X-ray detection characteristics of gold photocathodes and microchannel plates using synchrotron radiation (10 eV–82.5 keV)

Fast data acquisition system of a non-destructive profile monitor for a synchrotron beam by using a microchannel plate with multi-anodes

The image linearity of a charge division position readout anode, for instance, a Wedge and Strip Anode (WSA), is controlled by several factors. In addition to the drift field uniformity and pattern geometry requirements, linearity can be affected by the surface characteristics of the anode itself. We have undertaken experiments to establish the mechanisms which lead to non-linear response and suggest ways to avoid it. We present measured image non linearity of image intensifier tubes using two different types of charge division position readout anode; the Wedge and Strip anode (WSA) and the Spiral Anode (SPAN) devices. Both intensifier tubes were manufactured by DEP bv., Holland and utilize S20 or Caesium Telluride semi- transparent photocathodes on Magnesium Fluoride, Fused Silica or Calcium fluoride windows, proximity focused to a microchannel plate (MCP) stack. All detector variants built thus far use a stack of three MCPs in a Z configuration. We have undertaken experiments using a de- mountable detector of similar design but without window or photocathode. The role of secondary electrons produced on the anode in charge redistribution was investigated by using an intermediate conductive grid of high open area between the MCP and anode. The grid was used to define the electric field in a region just above the anode in order to either suppress the range of the anode secondary electrons, or prevent them from returning to the anode by collecting them on the grid. We present some preliminary results from these experiments and suggest modifications to the intensifier design to maximize the detector performance.

Using a micro channel plate (MCP), we have developed a sensitive method for measuring the onset of laser damage by detecting liberated surface ions and XUV radiation from the laser induced surface plasma. This method is insensitive to optical alignment and therefore assures good repeatability over numerous measurements.

We describe the design and development of the CHIPS microchannel plate detector. The Cosmic Hot Interstellar Plasma Spectrometer will study the diffuse radiation of the interstellar medium in the extreme ultraviolet band pass of 90Å to 260Å. Astronomical fluxes are expected to be low, so high efficiency in the band pass, good out-of-band rejection, low intrinsic background, and minimal image non-linearities are crucial detector properties. The detector utilizes three 75mm diameter microchannel plates (MCPs) in an abutted Z stack configuration. A NaBr photocathode material deposited on the MCP top surface enhances the quantum detection efficiency. The charge pulses from the MCPs are centroided in two dimensions by a crossed-delayline (XDL) anode. A four panel thin-film filter array is affixed above the MCPs to reduce sensitivity to airglow and scattered radiation, composed of aluminum, polyimide/boron, and zirconium filter panes. The detector is housed in a flight vacuum chamber to preserve the hygroscopic photocathode, the pressure sensitive thin-film filters, and to permit application of high voltage during ground test.

Extreme UV photodetectors based on CVD single crystal diamond in a p-type/intrinsic/metal configuration

The population of galaxies we see today is the result of billions of years of gas inflows, outflows, mergers, and feedback. To develop any holistic picture of the origin and evolution of galaxies, we thus need to understand their environments. The circumgalactic and intergalactic media (CGM and IGM) - the gas around and between galaxies, respectively - represent a large part of this environment. However, this gas is extremely faint and thus difficult to observe, and only recently have we been able to image it directly. This thesis presents instrumental and observational work focused on revealing galaxy environments in the early universe. Chapter 1 presents a brief history of our understanding of galaxies and an overview of our current picture of galaxy formation, including the role played by galaxy environments. In particular, it focuses on presenting the evolution of baryonic structures within a cosmological density field dominated by dark matter. Chapter 2 presents instrumental work on the Keck Cosmic Web Imager (KCWI, Morrissey et al. 2018), a new integral field spectrograph (IFS) for the Keck-2 10m telescope designed to study faint, extended emission. As an introduction, I discuss the advantages and disadvantages of integral field spectroscopy for the application of studying galaxy environments, as well as an overview of the prototype instrument - the Palomar Cosmic Web Imager (PCWI, Matuszewski et al. 2010). This chapter focuses primarily on engineering work during the development and testing of KCWI, though I conclude with a brief comparison of PCWI and KCWI performance in measuring the CGM around a high-redshift QSO. Chapter 3 presents the development of a software package designed to extract and analyze faint, extended emission in PCWI and KCWI data: CWITools. Although software is often an afterthought in astronomical and observational work, it is likely to become a primary barrier to conducting large IFS surveys of the CGM and IGM. This semi-automated analysis pipeline is presented and released publicly to empower future PCWI and KCWI studies. Chapter 4 presents the FLASHES (Fluorescent Lyman-α Structures in High-z Environments) pilot survey, published as O'Sullivan et al. 2020. The FLASHES pilot survey is an IFS study of extended HI Lyman-α emission in the environments of 48 z = 2.3 - 3.0 QSOs. The FLASHES Survey is the core project of this thesis, enabled by the instrumentation in Chapter 2 and the analysis pipeline developed in Chapter 3. The pilot survey represents the first statistically significant (N ≳ 30) sample of direct CGM observations in its redshift range. As such, it provides the first direct constraints on the 2D morphology, surface brightness profiles, and spatially resolved kinematics of the CGM during this period. Chapter 5 presents the first FLASHES follow-up study; deep IFS observations targeting extended Lyα 1216A, NV 1240A, CIV 1549A, and HeII 1640A emission from a subset of FLASHES pilot targets (O'Sullivan et al., in prep). Emission from metals in the CGM is expected to be an order of magnitude or more fainter than its Lyα, yet is a crucial ingredient in understanding the composition of the gas. Detecting this emission still requires multiple hours on 10m class telescopes. As such, large surveys of the multi-phase CGM remain extremely difficult to conduct. In this chapter, I present detections and upper limits of CGM metal emission around 8 FLASHES targets. Chapter 6 presents engineering work on FIREBall-2 (the Faint Intergalactic Redshifted Emission Balloon, second generation), a high-altitude UV telescope and IFS targeting CGM emission in the low-redshift universe (z ≃ 0.7). FIREBall-2 is an ambitious project deploying a novel, electron-multiplying CCD designed to achieve ≳ 50% quantum efficiency in the UV. This technology represents an order of magnitude increase in sensitivity from the microchannel plates used in the GALEX space telescope. FIREBall-2 serves as both an observational project in its own right, studying the low-z CGM, and a pathfinder mission for future UV space missions. Finally, Chapter 7 summarizes the contributions from this thesis and present a brief outlook on a few topics related to observations of galaxy environments.

Measurement of vectorial effects in the X-ray and UV photoemission from CsI: A novel polarimeter for soft X-ray astronomy