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Burning of coal will produce exhaust gases containing SOx compounds as well as NOx which can form acidic compounds such as H2SO4. When there is a decreasing in temperature as an effect of coal burning to reach the dew point so that will lead to corrosion, especially in the off gas line. This research was conducted to determine the effect of temperature to the corrosion rate of off-gas line material. The tested material was AISI SS 316L steel with temperature variation at 60°C, 70°C, 80°C, 90°C and 100°C. The corrosion rate tests were performed by weight loss method where the corrosive medium used to soak the steel was 3.5% NaCl solution of 500 ml and flowed by SO2 gas for 3 hours. From this corrosion rate testing, it was found that the corrosion rate increased along with the temperature increment where the highest corrosion rate was at the temperature of 100°C which is equal to 7,767,96950 mm/yr and included in very bad corrosion resistance level, beside that the steel sample color was also changed into black after immersion. The corrosion rate obtained at 80°C and 90°C showed poor corrosion resistance, while the corrosion rate at temperatures 60°C and 70°C are at very good and good level. This result was also shown by samples that were not change in color as well as at temperatures of 80°C, 90°C and 100°C. This research was also conducted to find out the temperature distribution model in off gas line by simulation in ANSYS software. From the simulation it was found that the decreasing in temperature began to occur in the ducting before the Electrostatic Precipitator (ESP) and continued to decrease down to the stack outlet.

Non-evaporable getter (NEG) coating is a technique to coat the inner walls of vacuum chambers with NEG thin films that can be activated through baking under ultrahigh vacuum (UHV). The activated NEG films suppress outgassing from the chambers and evacuate residual gasses, and consequently maintain UHV in the range 10–8 Pa with small ion pumps. The most widely-used NEG coating is deposited TiZrV films that can be fully activated after baking at 180 °C for 24 h. However, NEG coatings have rarely been applied to beamlines and endstations in synchrotron radiation facilities. To expand the scope of NEG coating applications, we developed a new NEG coating using oxygen-free Pd/Ti film deposition. The advantages of oxygen-free Pd/Ti coating are the following: 1) it can be activated by baking at 133–176 °C for 12 h; 2) it does not oxidize even after repeated venting-baking cycles; 3) it is potentially economical; 4) it does not require skilled technicians; 5) it can be applied to large chambers with a complex structure; and 6) it can be applied to narrow tubes where Pd and Ti filaments can be arranged. To investigate the thermal stability of oxygen-free Pd/Ti, we measured a series of X-ray photoelectron spectra of oxygen-free Pd(50 nm)/Ti(1 µm) film deposited on stainless steel 304L as a function of annealing temperature in the range 100–360 °C. Ti was found to segregate the surface and oxidizes forming Ti1+ at 280–300 °C. The results indicate that the maximum allowable temperature of oxygen-free Pd/Ti films is approximately 260 °C.Non-evaporable getter (NEG) coating is a technique to coat the inner walls of vacuum chambers with NEG thin films that can be activated through baking under ultrahigh vacuum (UHV). The activated NEG films suppress outgassing from the chambers and evacuate residual gasses, and consequently maintain UHV in the range 10–8 Pa with small ion pumps. The most widely-used NEG coating is deposited TiZrV films that can be fully activated after baking at 180 °C for 24 h. However, NEG coatings have rarely been applied to beamlines and endstations in synchrotron radiation facilities. To expand the scope of NEG coating applications, we developed a new NEG coating using oxygen-free Pd/Ti film deposition. The advantages of oxygen-free Pd/Ti coating are the following: 1) it can be activated by baking at 133–176 °C for 12 h; 2) it does not oxidize even after repeated venting-baking cycles; 3) it is potentially economical; 4) it does not require skilled technicians; 5) it can be applied to large chambers with a complex stru...

The twelve-strap high-harmonic fast-wave (HHFW) antenna on NSTX has exhibited a high-voltage standoff around 25 kV during previous experimental campaigns; this standoff needs to be improved for increased power coupling. During the recent NSTX-U upgrade period, a test-stand was set up with two antenna straps along with Faraday screens for testing purposes. Using a diagnostic suite consisting of a fast camera, a residual gas analyzer, a pressure gage, high-voltage probes, and an infrared camera, several interesting discoveries were made, leading to possible improvements of the antenna RF voltage operation level. First, arcing was observed outside the Faraday shields towards the low-voltage (“grounded”) end of the straps (faraday shield box ends); this arcing was successfully eliminated by installing an additional grounding point between the Faraday shield box and the vessel wall. Second, considerable outgassing was observed during the RF pulse and the amount of outgassing was found to decrease with increasi...

Spacecraft contamination has long been a subject of study in the rarefied gas dynamics community. Professor Mikhail Ivanov coined the term a spacecraft's "own ambient environment" to describe the effects of natural and satellite driven processes on the conditions encountered by a spacecraft in orbit. Outgassing, thruster firings, and gas and liquid dumps all contribute to the spacecraft's contamination environment. Rarefied gas dynamic modeling techniques, such as Direct Simulation Monte Carlo, are well suited to investigate these spacebased environments. However, many advances were necessary to fully characterize the extent of this problem. A better understanding of modeling flows over large pressure ranges, for example hybrid continuum and rarefied numerical schemes, were required. Two-phase flow modeling under rarefied conditions was necessary. And the ability to model plasma flows for a new era of propulsion systems was also required. Through the work of Professor Ivanov and his team, we now have a better understanding of processes that create a spacecraft's own ambient environment and are able to better characterize these environments. Advances in numerical simulation have also spurred on the development of experimental facilities to study these effects. The relationship between numerical results and experimental advances will be explored in this manuscript.

At CERN, the 160 MeV H− Linac4 will soon replace the 50 MeV proton Linac2. In the H− source two major sources of gas are identified. The first is the pulsed injection at about 0.1 mbar in the plasma chamber. The second is the constant H2 injection up to 10−5 mbar in the LEBT for beam space charge compensation. In addition, the outgassing of materials exposed to vacuum can play an important role in contamination control and global gas balance. To evaluate the time dependent partial pressure profiles in the H− ion source and the RFQ, electrical network – vacuum analogy and test particle Monte Carlo simulation have been used. The simulation outcome indicates that the pressure requirements are in the reach of the proposed vacuum pumping system. Preliminary results show good agreement between the experimental and the simulated pressure profiles; a calibration campaign is in progress to fully benchmark the implemented calculations. Systematic outgassing rate measurements are on-going for critical components in ...

Graphite is a widely used structural material for high temperature and high vacuum applications in furnaces handling corrosive materials or plasmas. The porosity, density, dimensions, impurities along with the history of graphitization, handling and storage of graphite dictate the outgassing characteristics. Graphite plates of density 1.78 g/cc were outgassed up to 1200 °C in vacuum of the order of 5×10−5 mbar in an in-house facility. A sample of the degassed graphite was taken for Thermo-Gravimetric Analysis (TGA). The TGA of the outgassed sample shows continuous weight loss in the temperature range of 200 °C to 1200 °C, indicating a much higher temperature is required for complete removal of gases. However, it may be noted that total outgassing is a function of the dimensions of the sample. The small coupon used in the TGA studies may not exactly replicate the large graphite blocks that outgases from the surface as well as from the bulk. The behaviour of graphite plates used in the liquid metal handling furnace where the graphite was finally used further confirmed this observation. The outgassing shown by the degassed graphite can be attributed to the diffusion of the absorbed gases from the bulk as well as desorption of the chemisorbed species which requires higher activation energies and higher temperature.

Modern ion implanters typically use dc arc discharge Plasma Electron Floods (PEFs) to neutralize wafer charge. The arc discharge requires using at least some refractory metal hardware, e.g. a thermionically emitting filament, which can be undesirable in applications where no metallic contamination is critical. rf discharge PEFs have been proposed to mitigate contamination risks but the gas flows required can result in high process chamber pressures. Axcelis has developed a microwave electron cyclotron resonance (ECR) PEF to provide refractory metals contamination-free wafer neutralization with low gas flow requirement. Our PEF uses a custom, reentrant cusp magnet field providing ECR and superior electron confinement. Stable PEF operation with extraction slits sized for 300 mm wafers can be attained at Xe gas flows lower than 0.2 sccm. Electron extraction currents can be as high as 20 mA at absorbed microwave powers < 70 W. On Axcelis' new medium current implanter, plasma generation has proven robust against pressure transients caused by, for example, photoresist outgassing by high power ion beams. Charge monitor and floating potential measurements along the wafer surface corroborate adequate wafer charge neutralization for low energy, high current ion beams.

To take full advantage of the high beam current capability of the Optima XEx on photoresist implants, a new, real-time uniformity correction scheme, IntelliScan, was developed. IntelliScan compensates for the dose asymmetry in beam-scan direction developed by charge exchange reactions due to severe photoresist outgassing. It continuously modifies the 1 KHz beam-scan waveform in real-time, according to instantaneous vacuum level in the angle corrector area. Since IntelliScan does not involve any extra steps in wafer handling, such as alternating 180° twist on every pass, high wafer throughput and implant angle integrity can be maintained throughout the entire implant process. This paper will describe the IntelliScan system and its performance on photoresist implants under extreme beam power conditions.

The Tropospheric Emission Spectrometer (TES) instrument pulse tube cryocoolers began operation 36 days after launch of the NASA Earth Observing System (EOS) Aura spacecraft on July 15, 2004. TES is designed with four infrared Mercury Cadmium Telluride focal plane arrays in two separate housings cooled by a pair of Northrup Grumman Aerospace Systems (NGAS) single-stage pulse tube cryocoolers. The instrument also makes use of a two-stage passive cooler to cool the optical bench. The instrument is a high-resolution infrared imaging Fourier transform spectrometer with 3.3-15.4 micron spectral coverage. After four weeks of outgassing, the instrument optical bench and focal planes were cooled to their operating temperatures to begin science operations. During the early months of the mission, ice contamination of the cryogenic surfaces including the focal planes led to increased cryocooler loads and the need for periodic decontamination cycles. After a highly successful 5 years of continuous in-space operations, TES was granted a 2 year extension. This paper reports on the TES cryogenic system performance including the two-stage passive cooler. After a brief overview of the cryogenic design, the paper presents detailed data on the highly successful space operation of the pulse tube cryocoolers and instrument thermal design over the past six years since the original turn-on in 2004. The data shows the cryogenic contamination decreased substantially to where decontamination cycles are now performed every six months. The cooler stroke required for constant-temperature operation has not increased indicating nearconstant cooler efficiency and the instrument's thermal design has also provided a nearly constant heat rejection sink. At this time TES continues to operate in space providing important Earth science data. KEYWORDS: TES, EOS, Aura, cryocooler

Ball Aerospace and Technologies Corporation (BATC) developed a unique thermal control coating named Ball InfraRed BlackTM (BIRBTM). The coating generates a highly diffuse surface with a large effective surface area ideal for thermal radiative applications. Independent testing demonstrates excellent emissivity properties across the cryogenic region, especially at temperatures

An accurate dose distribution control system was developed for a Nissin iG4 ion implanter, which is utilized for low temperature polycrystalline silicon thin film transistors (LTPS‐TFT), to improve dose uniformity under a photoresist outgas environment. The system consisted of a scan speed controller for glass substrates and monitors of ion beam flux to the target and pressure. To examine the performance, silicon wafers fixed on a glass sheet covered with photoresist were implanted. The dose uniformity was evaluated by measuring sheet resistance. Good uniformity was demonstrated with the use of the dose control under pressure variations of one order of magnitude.

Photoresist outgassing can significantly compromise accurate dosimetry of high energy implants. High energy implant even at a modest beam current produces high beam powers which create significantly worse outgassing than low and medium energy implants and the outgassing continues throughout the implant due to the low dose in typical high energy implant recipes. In the previous generation of high energy implanters, dose correction by monitoring of process chamber pressure during photoresist outgassing has been used. However, as applications diversify and requirements change, the need arises for a more versatile photoresist correction system to match the versatility of a single wafer high energy ion implanter. We have successfully developed a new dosimetry system for the Optima XE single wafer high energy ion implanter which does not require any form of compensation due to the implant conditions. This paper describes the principles and performance of this new dose system.

Oak Ridge National Laboratory (ORNL) is collaborating with Waukesha Electric Systems (WES) to develop a high‐temperature superconducting (HTSC) utility power transformer with primary and secondary coils cooled by liquid nitrogen. Since the vacuum‐insulated cryogenic coil dewar surrounds the magnetic core limb and cannot form a shorted turn, non‐conductive materials are required. Two test vessels and a small prototype dewar have been fabricated by Scorpius Space Launch Company with epoxy/fiberglass composites, using their proprietary PRESSURMAXX vessel technology. The effects of pumping time, bakeout temperature, and cryogenic vessel temperature on vacuum outgassing rates have been investigated. Outgassing rates of the individual materials used in vessel construction have also been measured. The results will be scaled up to determine the required pumping capacity for a full‐size 25‐MVA commercial transformer dewar.

Recent advancements in high energy laser (HEL) sources have outpaced diagnostic tools capable of accurately quantifying system performance. Diagnostic tools are needed that allow system developers to measure the parameters that define HEL effectiveness. The two critical parameters for quantifying HEL effectiveness are the irradiance on target and resultant rise in target temperature. Off‐board sensing has its limitations, including unpredictable changes in the reflectivity of the target, smoke and outgassing, and atmospheric distortion. On‐board sensors overcome the limitations of off‐board techniques but must survive high irradiance levels and extreme temperatures.We have developed sensors for on‐target diagnostics of high energy laser beams and for the measurement of the thermal response of the target. The conformal sensors consist of an array of quantum dot photodetectors and resistive temperature detectors. The sensor arrays are lithographically fabricated on flexible substrates and can be attached to...

The pressure distribution is an important aspect of a UHV subsystem in either a storage ring or a front end. The design of the 3‐GeV, 400‐mA Taiwan Photon Source (TPS) foresees outgassing induced by photons and due to a bending magnet and an insertion device. An algorithm to calculate the photon‐stimulated absorption (PSD) due to highly energetic radiation from a synchrotron source is presented. Several results using undulator sources such as IU20 are also presented, and the pressure distribution is illustrated.

The NEG‐coating, composed of ZrTiV with a lower temperature of activation, has been developed as a large surface getter pump for the aluminum (Al) chamber of small aperture and long length with a very poor conductance. However, the outgas of discharged gases, Ar or Kr, as well as the hydrocarbon molecules inside the NEG‐coated Al chamber has been observed. The desorption of the so‐called inert gases with heavier atomic mass residing inside the chamber results in the potential problem of higher cross section of scattering with the traveling beam hence reduces the life time seriously. To verify the outgas source of CH4, the NEG‐coated Al‐chamber exposed with heavy water (D2O) has been investigated. It shows the D2O and methane are the only outgases from the non‐coated Al chamber exposed with D2O. However, more outgas of CDxHy, CD4, and the C2DxHy complexes have been measured in the case of NEG‐coated Al chamber. Desorption of C2DxHy molecules can be reduced by exposing the NEG‐coated surface with synchrotro...

Experimental results on outgassing rates of patterned polymeric composites preliminary subjected to separate and combined radiation have been analyzed and presented. Mathematical models describing the outgassing processes in these materials were used for interpretation of the experimental data. Numerical results found using the models are presented.

Irradiation damage effects of the epoxy resin 648 and epoxy nano‐composites were studied by exposing them to vacuum ultraviolet irradiation (VUV) with wavelength varying from 5 nm to 200 nm. Experimental results obtained from mass loss, Scanning Electron Microscopy (SEM) and X‐ray Photoelectron Spectroscopy (XPS) show that nano‐TiO2 particles provide better resistance performance. Epoxy nano‐composite was found to be more advantageous over epoxy resin due to significant lower mass loss, lower flexural strength variation and the lower outgassing, with less gas component varieties after irradiation. In addition, now new carbon peaks were found and the principle components of the O ls peak did not change.

Organic materials are an essential part of the Advanced Stirling Convertor (ASC) construction as adhesives, potting, wire insulation, lubrication coatings, bobbins, bumpers, insulators, thread lockers. Since a long lifetime of such convertors to be used in the Advanced Stirling Radioisotope Generator (ASRG), sometimes up to 17 years, is required in various space applications such as Mars rovers, deep space missions, and lunar surface power, performance, durability and reliability of those organics should be critically evaluated in every possible material‐process‐fabrication‐service environment relations. The objective of this study was to evaluate, validate, and recommend organics for use in ASCs. Systematic and extensive evaluation methodologies were developed and conducted for various organic materials. The overall efforts dealing with organics materials for the last several years are summarized in the key areas, e.g., process‐fabrication optimization, adhesive bonding integrity, outgassing, thermal stability, and durability

The Optima XE is the first production worthy single wafer high energy implanter. The new system combines a state-of-art single wafer endstation capable of throughputs in excess of 400 wafers/hour with a production-proven RF linear accelerator technology. Axcelis has been evolving and refining RF Linac technology since the introduction of the NV1000 in 1986. The Optima XE provides production worthy beam currents up to energies of 1.2 MeV for P{sup +}, 2.9 MeV for P{sup ++}, and 1.5 MeV for B{sup +}. Energies as low as 10 keV and tilt angles as high as 45 degrees are also available., allowing the implanter to be used for a wide variety of traditional medium current implants to ensure high equipment utilization. The single wafer endstation provides precise implant angle control across wafer and wafer to wafer. In addition, Optima XE's unique dose control system allows compensation of photoresist outgassing effects without relying on traditional pressure-based methods. We describe the specific features, angle control and dosimetry of the Optima XE and their applications in addressing the ever-tightening demands for more precise process controls and higher productivity.

A high‐energy implanter process chamber and its pumping configuration were designed to minimize the residual gas density in the endstation. A modified Nastran™ finite‐element analysis (FEA) code was used to calculate the pressure distribution and gas flow within the process chamber. The modified FE method was readily applied to the internal geometry of the scan chamber, the corrector magnet waveguide, and the process chamber, which included the scan arm assembly, 300mm wafer, and plasma electron flood gun (PEF). Using the modified Nastran code, the gas flow and pressure distribution within the beamline geometry were calculated. The gas load consisted of H2, which is generated by photoresist (PR) outgassing from the 300mm wafer, and Xe from the plasma electron flood gun. Several pumping configurations were assessed, with each consisting of various locations and pumping capacities of vacuum pumps. The pressure distribution results for each configuration are presented, along with pumping efficiency results which are helpful in selecting the optimum pump configuration. The analysis results were compared to measured data, indicating a good correlation between the two.

The Karlsruhe Tritium Neutrino experiment (KATRIN) is an ambitious experiment to measure the electron neutrino mass from decay electrons of tritium with a sensitivity of 0.2 eV/c2. The length of the setup will be about 70 m, comprising an ultra luminous gaseous tritium source, a transport section with differential pumping, an electrostatic tandem spectrometer and a detector. The spectrometer section consists of two UHV vessels: i) the pre‐spectrometer with a diameter of 1.7 m and a length of 3.4 m acts as a pre‐filter for the large number of electrons entering from the source, ii) the main spectrometer with a length of 23.3 m and a diameter of 10m provides the necessary energy resolution of 1 eV. The high sensitivity requires a very low background rate of about 10 mHz. Among others this rate depends on the pressure inside the spectrometers, which are designed to maintain UHV conditions of 10−11 mbar or below.First prototype measurements with the smaller pre‐spectrometer (volume: 8.5 m3, surface: 25 m2) ha...

An analysis and reduction of outgassing in a high temperature superconductor (HTS) cable cryostat are very important to achieve operation over a long period of time. Because the outgassing surface area is much larger than the vacuum space of the cable cryostat, the vacuum condition of cable cryostat degrades quickly. A cold trap effect, where the activity of the molecules decrease in very low temperature, is observed when the cable cryostat is filled with liquid nitrogen (LN2). In this paper, the outgassing rate of HTS cable cryostat sample was measured for different vacuum insulation configuration with or without multilayer insulation (MLI), filled or not filled in cable cryostat LN2. And the test, which maintained the vacuum below 1.0×10−4 Torr was performed for 20 days.

A dedicated cold‐bore ion desorption experiment was performed in August 2004 at CERN’s Heavy Ion Accelerator LINAC 3. The dynamic outgassing of 4.2 MeV/u Pb53+ ions, impacting under 89.2° grazing incidence onto a copper tube, was studied as a function of the target temperature. Partial pressure rises of H2, CH4, CO, CO2, H2O, and O2 were measured at 300 K, 77 K, and 15 K using continuous lead ion bombardment. The new experimental setup is described and first pressure rise measurements are presented.A dedicated cold‐bore ion desorption experiment was performed in August 2004 at CERN’s Heavy Ion Accelerator LINAC 3. The dynamic outgassing of 4.2 MeV/u Pb53+ ions, impacting under 89.2° grazing incidence onto a copper tube, was studied as a function of the target temperature. Partial pressure rises of H2, CH4, CO, CO2, H2O, and O2 were measured at 300 K, 77 K, and 15 K using continuous lead ion bombardment. The new experimental setup is described and first pressure rise measurements are presented.

Outgassing measurements of three UHV materials (304 Stainless Steel (SS), 316L SS and 6061T‐6 aluminum) were made using the conductance and accumulation techniques as given in the AVS Recommended Practice for Outgassing Measurements [1]. Measurement results indicate good agreement between the two techniques. This study was undertaken to help determine the vacuum limitations of the photoelectron guns used at Jefferson Lab and to aid in the choice of vacuum chamber materials that will be used in the construction of future photoelectron guns. The outgassing rate measured for all of the chamber materials, regardless of technique, was about 1×10−12 Torr⋅1/s⋅cm2.

Hydrogen is the dominating gas specie in room temperature, ultrahigh vacuum systems of particle accelerators and storage rings, such as the Relativistic Heavy Ion Collider (RHIC) at Brookhaven. Rapid pressure increase of a few decades in hydrogen and other residual gases was observed during RHIC’s recent high intensity gold and proton runs. The type and magnitude of the pressure increase were analyzed and compared with vacuum conditioning, beam intensity, number of bunches and bunch spacing. Most of these pressure increases were found to be consistent with those induced by beam loss and/or electron stimulated desorption from electron multi‐pacting.

Hydrogen is the predominant residual gas in metal vacuum systems at very low pressures (i.e. in the utrahigh [uhv] and extreme high vacuum [xhv] ranges) and the reduction in the hydrogen outgassing rate is the most challenging problem in achieving xhv. Our understanding of the diffusion and adsorption/desorption processes involved in the outgassing of hydrogen from metals has much improved in recent years and has led to better methods for reducing the outgassing rates of hydrogen from metals such as stainless steel and aluminum alloys. This overview examines some recent advances in our understanding of the effects of hydrogen in vacuum systems; these include a) the adsorption/desorption/diffusion equilibrium at the vacuum-metal interface, b) the effects of multiple energy states of H atoms in the bulk metal, c) the physical adsorption of hydrogen on surfaces at cryogenic temperatures and d) the anomalous effects in pressure measurements of hydrogen with ionization gauges and residual gas analyzers., First International Workshop on Hydrogen in Materials and Vacuum Systems, November 11-13, 2002, Newport News, Virginia, USA, Series: AIP Conference Proceedings; no. 671

The stainless steel vacuum chambers of the 248m accumulator ring of Spallation Neutron Source (SNS) are coated with ∼ 100 nm of titanium nitride (TiN) to reduce the secondary electron yield. The coating is produced by DC magnetron sputtering using a long cathode imbedded with permanent magnets. The outgassing rates of several SNS half‐cell chambers were measured with and without TiN coating, and before and after in‐situ bake. One potential benefit of a TiN coating is to serve as hydrogen permeation barrier that reduces the ultimate outgassing rate. By varying the coating parameters, films of different surface roughness were produced and analyzed by Auger electron spectroscopy, scanning electron microscopy and atomic force microscopy to illustrate the dependence of the outgassing on the film structure.

As ULSI technology continues to advance, semiconductor manufacturers are facing new contamination control and monitoring challenges, including airborne molecular contamination (AMC). AMC is being recognized as one of the yield limiting factors in newer generation microelectronics fabrication processes. A major AMC source, materials’ outgassing can introduce a variety of organic contaminants into semiconductor fabs, impacting many processes. This paper provides a brief overview of typical organic outgassing contaminants, their sources, process impacts and analytical techniques used to detect these species. In addition, outgassing study results for polycyclodimethylsiloxanes and several other contaminants using thermal desorption‐gas chromatography‐mass spectrometry (TD‐GC‐MS) analysis are employed to demonstrate the relationships among (1) outgassing level and outgassing time (linear), (2) outgassing quantity and the inverse of outgassing temperature (logarithmic), and (3) outgassing quantity and material surface area (linear). A new method, based on gas diffusion conductivity detection, for ammonia and volatile amines’ outgassing analysis is also presented.

A continuous‐duty hydrogen sorption cryocooler is being developed for the Planck spacecraft, a mission to map the cosmic microwave background beginning in 2007. This cryocooler uses six individual compressor elements (CEs) filled with the hydriding alloy LaNi4.78Sn0.22 to provide high‐pressure (50 bar) hydrogen to a Joule‐Thomson (J‐T) expander and to absorb low‐pressure (∼0.3 bar) gas from liquid hydrogen reservoirs cooled to ∼18K. Quadrupole Mass Spectrometry (QMS) showed methane in these hydride beds after cycling during initial operation of laboratory tests of the Planck engineering breadboard (EBB) cooler. These contaminants have caused problems involving plugged J‐T expanders. The contaminants probably come from reactions with residual hydrocarbon species on surfaces inside the hydride bed. The hydride bed in each CE is contained in an annular volume called a “gas‐gap heat switch,” which serves as a reversible, intermittent thermal path to the spacecraft radiator. The gas‐gap is either “off” (i.e., its pressure

Achieving Ultra High and Extreme High Vacuum without high temperature bakeouts is becoming essential in many applications. In this study, we investigated the use of inexpensive silica and titanium oxide thin film coatings on vacuum chambers/components to reduce the adsorption of water on the chamber walls. Water can be cracked into oxygen and hydrogen in the material and act as one of the sources of hydrogen. The measured outgassing rates of the stainless steel chambers with the thin film barrier coatings are in the range 1×10−12 Torr 1/s cm2 to 2.5×10−13 Torr 1/s cm2. We have also backed the turbo pump with an ion pump to understand and plan for fast pump down of vacuum systems.

Commercially available inexpensive and rugged miniature Stirling cryocoolers are frequently used in sophisticated infrared imagers. Such coolers are well known sources of high-frequency interference contaminating the image signal and causing essential degradation in the overall imager performance. This phenomenon is generally referred to as microphonics, which mostly manifests itself at the resonant frequencies of sensitive mechanical components of infrared packages. The ruggedizing of these components involves stiffening and dampening which are, evidently, not the best solutions for implementation inside, say, an evacuated envelope, where the issues of added heat load, thermal mass, ageing, vacuum contamination due to outgassing are of the primary concern. The paper examines the idea of using externally mounted wideband dynamic absorbers for suppressing the above resonant responses and microphonic noise. The analytical model suggested relies on a set of complex frequency response functions experimentally measured on the original infrared package. The optimised dynamic absorber yields about a tenfold reduction in the amplification ratio at typical resonant frequencies and a threefold reduction in the overall rms level of microphonic noise. The results of the analytical calculation are in fair agreement with experimental data.

Ongoing experimental work and theoretical models indicate that milliwatt thermoelectric generators that operate in a sealed-off vacuum environment will be useful for long-term operation, such as the PASCAL 20 year Mars mission and the CryoScout mission. Considerations for long-term operation include out gassing of the multifoil vacuum insulation before pinch off and vaporization of the (Bi, Sb)2(Se, Te)3 thermoelectric materials during long-term operation. Tests underway indicate the multi-foil insulation can be pre-outgassed before assembly so further outgassing in the sealed generator is minimized. Experimental data and vaporization models for a Th of 250 °C thus far indicate that the small amount of vaporization of materials used in the thermoelectric module do not significantly effect the generator vacuum or the module power output. These tests and models indicate that both potential modes of degradation can be controlled and minimized. Although performance data on the generator materials only extend ...