[en] Atomic beam sources (ABS) are widely used workhorses producing polarized atomic beams for polarized gas targets and polarized ion sources. Although they have been used for decades the understanding of the beam formation processes is crude. Models were used more or less successfully to describe the measured intensity and beam parameters. ABS's are also foreseen for future experiments, such as PAX [1]. An increase of intensity at a high polarization would be beneficial. A direct simulation Monte-Carlo method (DSMC)[2] was used to describe the beam formation of a hydrogen or deuterium beam in an ABS. For the first time a simulation of a supersonic gas expansion on a molecular level for this application was performed. Beam profile and Time-of-Flight measurements confirmed the simulation results. Furthermore a new method of beam formation was tested, the Carrier Jet method [3], based on an expanded beam surrounded by an over-expanded carrier jet.

[en] At the SpinLab test stand (University of Ferrara), the elastic scattering cross section for molecular hydrogen has been determined for relative velocities in the range 1500-3000 m/s from the measured attenuation of a beam traversing a chamber of rest gas. This cross section is a fundamental input for simulations of gas flows in an atomic beam source with the Direct Simulation Monte Carlo method. Both the predicted beam intensity and width of the beam's velocity distribution are sensitive to the cross section value, and agreement with the measured values is demonstrated for the first time. The simulations also predict properties of the expansion that are difficult to access experimentally, namely a peaking factor of 1.45±0.05 that is essentially independent of input flow in the range 25-250 sccm, and an increase in the beam divergence at the skimmer exit for higher input flows

[en] Two new test bench studies have deepened the understanding of polarized gas targets and the atomic beam sources (ABS) that fill them. The attenuation coefficient for beam loss due to rest gas scattering has been measured over a range of beam velocities. The total scattering cross sections can be extracted from these measurements for the first time. Low conductance injection tubes have the potential to increase the thickness of storage cell targets. Injection tubes with internal fins were characterized, and the beam loss at the tube exit was larger than expected. Beam simulations agree with the measured intensity loss only when the atoms' trajectories have a non-zero azimuthal velocity component.

[en] Liquid Argon Time Projection Chambers (LArTPCs) show promise as scalable devices for the large detectors needed for long-baseline neutrino oscillation physics. Over the last several years at Fermilab a staged approach to developing the technology for large detectors has been developed. The TPC detectors require ultra-pure liquid argon with respect to electronegative contaminants such as oxygen and water. The tolerable electronegative contamination level may be as pure as 60 parts per trillion of oxygen. Three liquid argon cryostats operated at Fermilab have achieved the extreme purity required by TPCs. These three cryostats used evacuation to remove atmospheric contaminants as the first purification step prior to filling with liquid argon. Future physics experiments may require very large detectors with tens of kilotonnes of liquid argon mass. The capability to evacuate such large cryostats adds significant cost to the cryostat itself in addition to the cost of a large scale vacuum pumping system. This paper describes a 30 ton liquid argon cryostat at Fermilab which uses purging to remove atmospheric contaminants instead of evacuation as the first purification step. This cryostat has achieved electronegative contamination levels better than 60 parts per trillion of oxygen equivalent. The results of this liquid argon purity demonstration will strongly influence the design of future TPC cryostats

[en] At the SpinLab laboratory (University of Ferrara, Italy), a three stage cooling system was installed along the dissociator tube of an atomic beam source (ABS). With this tool, it is possible to observe correlations between the measured temperatures and the atomic beam intensity. The existence of such correlations is suggested by the larger intensity of the RHIC ABS, the only other source with additional cooling stages. An increased intensity at lower cooling temperatures was observed in SpinLab, while no change in the beam's velocity distribution was observed

[en] The setup of the polarized target for the spin filtering studies at COSY and AD will be shown together with the planned measurements. The target fulfills all the requirements coming from the experiment

[en] The storage cell of the internal, longitudinally polarized, atomic gas target of the Hermes experiment is presented. The polarized atoms of hydrogen or deuterium are accumulated in an open-ended thin walled storage cell through which the circulating electron or positron beam of the HERA accelerator passes. The target areal density is 10¹⁴ atoms/cm², two orders of magnitude larger than without the cell. The construction details of the cell are described and the cell's performance during HERMES run of 1997-2000 is discussed

[en] A gas analyzer has been developed for the internal polarized target of the HERMES experiment at DESY in order to determine the relative amount of atomic and molecular hydrogen or deuterium in a gas sample. The precise quantitative knowledge of this ratio is crucial because the nucleons in atoms and molecules contribute differently to the average nuclear polarization of the target gas. A new calibration technique used to derive the relative sensitivity to atoms and molecules is presented. As an example, it is shown how the gas analyzer is used within the HERMES environment to divide the molecules in the gas sample into an unpolarized and a potentially polarized fraction

[en] The spin-exchange collision cross-section for hydrogen atoms has been measured for the first time in the low temperature range 40-100 K by using the polarized hydrogen gas target of the Hermes experiment at DESY (Hamburg, Germany). The results agree with a previous measurement in the overlapping temperature region 80-100 K, while seem to hint an increasing behaviour with temperature in the region 50-80 K. (authors)

[en] In this paper, we report on the design and operation of the LongBo time projection chamber in the Liquid Argon Purity Demonstrator cryostat. This chamber features a 2 m long drift distance. We measure the electron drift lifetime in the liquid argon using cosmic ray muons and the lifetime is at least 14 ms at 95% confidence level. LongBo is equipped with preamplifiers mounted on the detector in the liquid argon. Of the 144 channels, 128 channels were readout by preamplifiers made with discrete circuitry and 16 channels were readout by ASIC preamplifiers. For the discrete channels, we measure a signal-to-noise (S/N) ratio of 30 at a drift field of 350 V/cm. The measured S/N ratio for the ASIC channels was 1.4 times larger than that measured for the discrete channels