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PartTec, Ltd. has, for the past 3 years, pursued the development of 3He alternative neutron detectors for applications such as border security, portal monitors and handheld devices. This paper discusses PartTec's mobile, very large area, ruggedized and highly efficient neutron detector. The detector's construction and performance are outlined in the paper. The goals for development of the detector are to meet all performance standards of the ANSI N42.43 committee's publication, “American National Standard Performance Criteria for Mobile and Transportable Radiation Monitors Used for Homeland Security.” The introductory model of PartTec's line of mobile neutron detectors has an active area of 3,600 cm2, consists of 1,200 wavelength shifting fibers, 12 single anode photomultiplier tubes and 60cm × 60cm 6LiF:ZnS(Ag) scintillator sheets. The purpose of the paper is to introduce to the community the successful implementation of the use of LiF scintillator-based neutron detectors in real-world applications, showing that a commercially viable helium-3 replacement can now be developed. The paper discusses issues related to this detection technology including its performance, manufacture, availability, design flexibility, and cost. [ABSTRACT FROM PUBLISHER]

The NIST numerical software, REGEN3.3, which incorporates both He-4 and He-3 properties, was used to calculate the losses and second law efficiencies of 4 K regenerators operating at 30 Hz. Operating parameters, such as average pressure, pressure ratio, and warm-end temperature were varied to investigate the effect of non-ideal gas properties. Regenerator parameters such as matrix material and shape, hydraulic diameter, and regenerator geometry were varied to investigate losses due to non-ideal regenerator behavior. The results show that He-3 can increase the regenerator efficiency by a factor of at least two compared to a regenerator optimized for He-4. A layered regenerator of gadolinium oxysulfate (GOS) at the cold end and ErPr at the warm end is the best of many material combinations. A regenerator with parallel holes of about 20% porosity showed only slight improvement over one with packed spheres. The regenerator warm-end temperature has little effect on its efficiency for temperatures below 35 K and pressures of 1.0 MPa and above. An optimized 4 K He-3 regenerator uses layered GOS and ErPr with the warm end at about 30 K and an average pressure of about 1.0 MPa. With those optimum conditions a reduced regenerator loss of 0.36 and a regenerator second law efficiency of 25% are achieved. [ABSTRACT FROM AUTHOR]

Neutron detection is an essential aspect of interdiction of radiological threats for national security purposes, since plutonium, a material used for nuclear weapons, is a significant source of fission neutrons. Radiation portal monitoring systems, of which there are thousands deployed for homeland security and non-proliferation purposes, currently use ³He gas-filled proportional counters for detecting neutrons. Because of the high usage of ³He for neutron scattering science and national security, the supply has dwindled, and can no longer meet the demand. Consequently, a replacement technology for neutron detection is required in the very near future. [ABSTRACT FROM AUTHOR]

Since the introduction of hyperpolarized 3He and 129Xe as gaseous MRI contrast agents more than a decade ago, a rich variety of imaging techniques and medical applications have been developed. Magnetic resonance imaging of the inhaled gas depicts ventilated lung airspaces with unprecedented detail, and allows one to track airflow and pulmonary mechanics during respiration. Information about lung structure and function can also be obtained using the physical properties of the gas, including spin relaxation in the presence of oxygen, restricted diffusion inside the alveolar airspaces, and the NMR frequency shift of xenon dissolved in blood and tissue. [ABSTRACT FROM AUTHOR]

We have developed a thermal-neutron coded-aperture imager that reveals the locations of hydrogenous materials from which thermal neutrons are being emitted. This imaging detector can be combined with an accelerator to form an active interrogation system in which fast neutrons are produced in a heavy metal target by means of excitation by high energy photons. The photo-induced neutrons can be either prompt or delayed, depending on whether neutron-emitting fission products are generated. Provided that there are hydrogenous materials close to the target, some of the photo-induced neutrons slow down and emerge from the surface at thermal energies. These neutrons can be used to create images that show the location and shape of the thermalizing materials. Analysis of the temporal response of the neutron flux provides information about delayed neutrons from induced fission if there are fissionable materials in the target. The combination of imaging and time-of-flight discrimination helps to improve the signal-to-background ratio. It is also possible to interrogate the target with neutrons, for example using a D-T generator. In this case, an image can be obtained from hydrogenous material in a target without the presence of heavy metal. In addition, if fissionable material is present in the target, probing with fast neutrons can stimulate delayed neutrons from fission, and the imager can detect and locate the object of interest, using appropriate time gating. Operation of this sensitive detection equipment in the vicinity of an accelerator presents a number of challenges, because the accelerator emits electromagnetic interference as well as stray ionizing radiation, which can mask the signals of interest. [ABSTRACT FROM AUTHOR]

We have constructed a vertical cylindrical cell in which we cool superfluid 3He to the low temperature limit. At the top and bottom of this cylinder are pairs of vibrating wire resonators (VWRs), one to act as a heater and the other as a thermometer. Quasiparticle excitations are created by driving the heater VWRs. These excitations can only leave the cylinder via a small hole at the top. Using a shaped magnetic field, we can produce a layer of A phase across the tube, while maintaining low field B phase in the vicinity of the VWRs for reliable thermometry. Preliminary results show that the two A-B interfaces lead to a measurable extra resistance for quasiparticles between the top and bottom of the cylinder. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

In the temperature range below 0.2Tc, the gas of thermal excitations from the superfluid 3He-B ground state is in the ultra-dilute ballistic regime. Here we discuss preliminary measurements of the transport properties of this quasiparticle gas in a cell of cylindrical geometry with dimensions much smaller than any mean free path. The vertical cylinder, constructed from epoxy-coated paper, has vibrating wire resonator (VWR) heaters and thermometers at the top and bottom, and a small aperture at the top which provides the only exit for quasiparticles. Using the thermometer VWRs, we measure the difference in quasiparticle density between the top and bottom of the tube when we excite the top or bottom VWR heater. This gives information about the transport of energy along the cylindrical 3He sample and hence about the scattering behaviour involved when a quasiparticle impinges on the cylinder wall. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

From our long experience of using profiled magnetic fields to stabilize and manipulate the A-B phase boundary in superfluid 3He, we have constructed a cell in which we can create and move a droplet of B phase, levitated within A phase away from any walls at T ∼ 0.15Tc. Uniquely, the A and B condensates are coherent across the A-B interface and at such low temperatures the superfluid is essentially pure, providing the most ordered phase boundary to which we have laboratory access. We configure the field so that within a bulk volume of superfluid, a region of high field (stabilizing the A phase) completely surrounds a region of lower field (stabilizing the B phase). Our preliminary measurements are at zero pressure and temperatures below 0.3Tc where the first-order transition from B to A phase is at 340 mT. We observe the formation of the droplet as we ramp the field, and we also study the transport of thermal excitations out of the droplet. Future plans include measurements at higher pressures where the A phase can be stabilized in low magnetic field at temperatures close to Tc. Upon cooling into the B phase we should then be able to make the first studies of nucleation uninfluenced by the presence of container walls. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

We have measured the onset of quantum turbulence generated by a vibrating grid resonator in 3He-B. Our measurements were carried out in the low temperature regime where the normal fluid component is very dilute and can be described as a gas of ballistic quasiparticles. Consequently, the normal fluid component can not participate in turbulence generation. We have measured the onset of turbulence from the grid motion using two nearby vibrating wire resonators. The vibrating wires show a reduction in thermal quasiparticle damping due to Andreev reflection in the surrounding turbulent velocity field. Our measurements reveal a transition in the transient behavior of the onset of the vorticity signal at the vibrating wire resonators as a function of the grid velocity. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]