Fusion vacuum systems for processing of deuterium and tritium pose safety hazards by formation of potentially explosive mixtures in case of air inleakage. Early detection of such hazards is essential ...for the safety of process equipment for fuel purification and recycling. Having established the fact that conventional oxygen monitors do not work well in hydrogen atmospheres at low pressures, we developed a sensor compatible with this duty. It is based on the detection of the oxygen-hydrogen reaction heat in a differential thermoelectric calorimeter, using a proprietary AECL wetproof catalyst for promoting the recombination reaction and semi-conductor thermopiles for detection. Operating at room temperature, the sensor provides signals in excess of 1 mV for explosive hydrogen-air mixtures at pressures as low as 1 mbar. The differential principle employed suppresses erroneous signals originating from hydrogen sorption/desorption heat on the catalyst.
The JET Active Gas Handling System is designed for processing of the exhausts from the JET Torus and its ancillaries to enable tritium to be recycled through the machine. The design concept was ...established in mid 1987 and site installation is essentially complete. This paper describes the measures and solutions which were adopted for achieving construction standards and gaining approval for operation of such plant.
We demonstrate an efficient scheme for continuous trap loading based upon spatially selective optical pumping. We discuss the case of \(^{1}\)S\(_{0}\) calcium atoms in an optical dipole trap (ODT), ...however, similar strategies should be applicable to a wide range of atomic species. Our starting point is a reservoir of moderately cold (\(\approx 300 \mu\)K) metastable \(^{3}\)P\(_{2}\)-atoms prepared by means of a magneto-optic trap (triplet-MOT). A focused 532 nm laser beam produces a strongly elongated optical potential for \(^{1}\)S\(_{0}\)-atoms with up to 350 \(\mu\)K well depth. A weak focused laser beam at 430 nm, carefully superimposed upon the ODT beam, selectively pumps the \(^{3}\)P\(_{2}\)-atoms inside the capture volume to the singlet state, where they are confined by the ODT. The triplet-MOT perpetually refills the capture volume with \(^{3}\)P\(_{2}\)-atoms thus providing a continuous stream of cold atoms into the ODT at a rate of \(10^7 \)s\(^{-1}\). Limited by evaporation loss, in 200 ms we typically load \(5 \times 10^5\) atoms with an initial radial temperature of 85 \(\mu\)K. After terminating the loading we observe evaporation during 50 ms leaving us with \(10^5\) atoms at radial temperatures close to 40 \(\mu\)K and a peak phase space density of \(6.8 \times 10^{-5}\). We point out that a comparable scheme could be employed to load a dipole trap with \(^{3}\)P\(_{0}\)-atoms.
The Product Storage (PS) and Intermediate Storage (IS) systems of the Active Gas Handling System (AGHS) are hydrogen isotope storage facilities. IS will take pure hydrogen mixtures from the Cryogenic ...Forevacuum (CF) system and store them until the isotope separation systems, Cryogenic Distillation (CD) and Gas Chromatography (GC), are ready to separate the mixtures into pure H
2
, D
2
and T
2
. The purified D
2
and T
2
will be sent to PS for storage, while any protium will be diluted with nitrogen and discharged to atmosphere if the T
2
levels are below 4 × 10
−4
Ci/m
3
. PS will then deliver gas via the Gas Introduction (GI) system to the various users. The principal parts of PS and IS are their U-bed assemblies. Each assembly consists of four uranium beds (U-bed) which each store up to 27 moles of hydrogen. The commissioning results, the absorption and desorption characteristics of the U-beds, the sequences for safe operation of the U-beds and transfer of gases to other AGHS systems, the hardwired interlock system and the over/underpressure protection system for the secondary containments will be discussed.
Metastable calcium atoms, produced in a magneto-optic trap (MOT) operating
within the singlet system, are continuously loaded into a magnetic trap formed
by the magnetic quadrupole field of the MOT. ...At MOT temperatures of 3 mK and
240 ms loading time we observe 1.1 x 10^8 magnetically trapped 3P2 atoms at
densities of 2.4 x 10^8 cm^-3 and temperatures of 0.61 mK. In a modified scheme
we first load a MOT for metastable atoms at a temperature of 0.18 mK and
subsequently release these atoms into the magnetic trap. In this case 240 ms of
loading yields 2.4 x 10^8 trapped 3P2 atoms at a peak density of 8.7 x 10^10
cm^-3 and a temperature of 0.13 mK. The temperature decrease observed in the
magnetic trap for both loading schemes can be explained only in part by trap
size effects.
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