AVS2013 Session VT-TuP: Vacuum Technology Poster Session and Student-Built Vacuum System Poster Competition
Tuesday, October 29, 2013 6:00 PM in Room Hall B
Tuesday Evening
Time Period TuP Sessions | Topic VT Sessions | Time Periods | Topics | AVS2013 Schedule
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VT-TuP-1 A Study of Uncertainties at Calibration of Helium Leak Calibrator
YuWei Lin, ChienPao Lin, Chien-Nan Hsiao, FongZhi Chen (National Applied Research Laboratories, Taiwan, Republic of China) Helium leak calibrator is used throughout industry for calibration of leak detectors. A calibration system for helium leak calibrator is developed, and the range of calibration is from 10−6 to 10−7 std* cc/s. The origins of the entire system’s uncertainty may be divided into two categories, type A and type B. Type A uncertainty can be determined by making use of a statistical methodology to treat the statistical data of normal distribution and come up with the average standard deviation. The measurement repetitiveness of a set of 35 acquired calibration data was evaluated and reported in the study, and the quantitative value is a measure for the system’s stability. Type B uncertainty includes tracing back the national laboratory (national institute standards and technology, NIST), resolution of Helium leak calibrator, temperature effect, and impurities of working gas. The present estimate of the total uncertainty in the measured leak rate of this artifact at 23℃ at the time of test is 5.2%. This includes a systematic uncertainty of 2.0% in flow meter of the NIST primary Leak standard and 3.2% random errors in the measured leak rate of this artifact. The errors represent three standard deviations. Declared is the relative expanded uncertainty (U) which resulted from the relative standard uncertainty multiplied by the coverage factor k=2. The uncertainty is calculated according to the “Guide to the Expression of Uncertainty in Measurement”. In regular cases it can be assumed that the value of the measure lies with a level of confidence of approximately 95％ within the specified interval. The present research has demonstrated the high stability and great efficacy of the calibration system for helium leak calibrator. |
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VT-TuP-2 Performance Measurements of Scroll Pump
Fan-Chun Hsieh, Ping-Hung Lin, Chih-Wen Chen, Jiann-Shiun Kao, FongZhi Chen (National Applied Research Laboratories, Taiwan, Republic of China) Scroll pumps are widely used in solar-optic and semiconductor industry for backing purpose. The performance of scroll pump could affect significantly the performance of pumping station. Here, a condition monitoring of scroll pump was developed and monitored through LabVIEW. The pumping speed, acceleration, and noise level were measured for mass flow rate ranges from 50 to 200 sccm (standard cubic centimeter per minute). The pumping speed increases sharply and almost linearly when inlet pressure smaller than 0.307 mbar. The RMS magnitude of acceleration shows a maximum peak which occurs at about 30 Hz. Moreover, small peaks were observed in the spectrum because of the reciprocating motion of the pump. The noise level fluctuates obviously at inlet pressure approaches 1 mbar. The proposed measurements provide a considerable advancement in diagnosis development of pump. |
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VT-TuP-4 Vacuum Thermal Oxidation of a Stainless Steel Vacuum Chamber Following Citric Acid Cleaning
Taekyun Ha, Sukmin Chung, ChongDo Park (POSTECH, Republic of Korea) We perform vacuum thermal oxidation with a stainless steel vacuum chamber after citric acid cleaning to reduce the outgassing rate. Pure and dense chromium oxide layer on the surface of the stainless steel is considered to be a diffusion barrier for hydrogen atoms from the bulk. How to form such a high quality chromium oxide layer onto the surface is the key to reduce hydrogen outgassing and to reach extreme high vacuum with stainless steel vacuum systems. The vacuum thermal oxidation at 450oC in vacuum with low oxygen partial pressure is a proven treatment for that. We enhance the purity of the chromium on the surface of the stainless steel by citric acid cleaning before this vacuum thermal oxidation using the property that the citric acid is effective to reduce surface iron contents. The surface analysis results and the vacuum characteristics for this treatment are discussed in this paper. |
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VT-TuP-5 Operation Status of the PLS-II Photon Absorbers
Taekyun Ha, ChongDo Park (POSTECH, Republic of Korea) The PLS-II storage ring photon absorbers are designed to accommodate the high heat load from the stored beam with 3 GeV beam energy and 400 mA beam current. Two temperature sensors are attached on the lower and upper part of the photon absorber body near to the thermally most severe point, which are placed inside the vacuum chamber. We report the operation status of the photon absorbers since the start of the commissioning in 2011. First, we compare the calculated temperature values with the measured ones during the beam stored up to 100 mA. From this results, we can estimate the temperature of the photon absorbers with 400 mA beam current more accurately. Second, We estimate the electron beam position by measured temperature differences between the upper and lower sensors. The results are compared with the measured values from the beam position monitor. |
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VT-TuP-7 A Novel Differential Pump for the NSLS-II Project Soft X-Ray Beamline
Jih-Perng Hu, Daniel Bacescu, Chris Stelmach (Brookhaven National Laboratory); Marcelo Ferreira (SLAC National Accelerator Laboratory); Richard Greene, Cecilia Sanchez Hanke (Brookhaven National Laboratory) An innovative differential pump is designed to maintain/preserve the ultra-high vacuum (UHV) conditions at the upstream side, and to provide adequate UHV conditions on the downstream side to preserve and maintain the surfaces of the optical components free of contaminants that affect negatively the performance of the beamline. Additionally the differential pump compact design, ~500 mm (flange to flange) in length, allows the photon beam to pass through the ion pump active area delaying and moderating the potential leak-induced vacuum shock wave expanding and venting either side of the beamline. The straight narrow inlet and outlet throttles of the differential pump assembly, reach into the core of the pump limiting the conductance of the gas flow. The upstream throttle consist of an externally water cooled GlidCop® body with an internal rectangular tapered aperture able to dissipate the heat load of the mis-steered white beam coming generated at the source and collimated at the front end. This asymmetric differential pump was fabricated by Gamma Vacuum, LLC (presently Edwards Technology). With adjustments on size, cooling and pumping, the prototype differential pump can be tailored for beamline sections at high vacuum or ultra-high vacuum. Details of pump design and bench testing will be presented. Work performed was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886. |
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VT-TuP-8 Measurement of Low Outgassing Rates using Quadrupole Mass Spectrometers
D.L. Seymour, S. Davies, J.A. Rees (Hiden Analytical) Measurements of the total outgassing rates of UHV chambers are often limited to around 1x10E-13 Torr-litres per sec by the outgassing rates of the vacuum gauges used to monitor the behaviour of the vacuum chamber and by possible thermal desorption caused by heating of the chamber walls by the gauges. The use of quadrupole mass spectrometer instruments to monitor the outgassing of vacuum chambers, including those used in plasma processing systems, is of interest both because the minimum measureable outgassing rate may be lower and because the mass spectrometer data provides partial outgassing rates for individual gas components. This more detailed description of the outgassing process gives a better historical record of the behaviour of a particular system, and can readily follow, for example, changes from outgassing dominated by water vapour to a regime where the dominant outgassing gas is hydrogen. Increased sophistication may be added to the mass spectrometric measurements by adopting threshold ionisation techniques in which the use of electron energies well below those normally employed in QMS instruments can be used to distinguish between gases , such as nitrogen and carbon monoxide, that have nominally the same mass peak at m/q =28. New measurements carried out using a high sensitivity instrument are reported which illustrate the power of such procedures and, in particular, help resolve outstanding problems such as the identity and origins of the mass peak at m/q =19 in RGA data for UHV systems. |