Andrzej K. Drukier

Planar array of superheated superconductors: An improved superheated superconducting granule detector

We have invented a new superheated superconducting granule detector which is a prime candidate for sensing dark matter and which could prove very useful for other applications. The sensor element is a planar array of spherical granules for which the spread in transition temperatures is nearly an order of magnitude smaller than that for a colloidal device. The detecting efficiency for low‐energy deposition is thereby significantly increased. Preliminary results are described.

Recent developments in superheated superconducting granular detectors

Abstract The operation of a superheated superconducting granular detector with a SQUID readout is described, and the advantages and limitations of the colloidal device discussed. A new sensor consisting of a planar array of granules is described and results demonstrating an order of magnitude decrease in the spread of transition temperatures are presented.

Neutron detection using a planar array of superheated superconductors

Abstract A new thermal neutron detector consisting of an indium/mylar PASS array with a filler of boron powder has been tested successfully. A boron nucleus captures a neutron and the α-particle emitted in this reaction nucleates the transition to the normal state in a neighbouring grain. A PASS with grain radius r = 12 μ m showed very low response to irradiation by 835 keV γ-rays. The same PASS responded to α-particles with high efficiency, and thermal neutrons were detected with good efficiency and very low background. Thermal neutrons were also counted with an R = 25 μ m PASS. The use of large granules will allow spatial resolution to a single grain to be obtained and a read-out based on conventional inductive coupling and fast electronics to be utilized.

The position sensitivity of a planar array of superheated superconductors

Abstract A new technique for manufacturing the superheated superconducting granule detector is reported. The new sensor element has the potential for position sensitive detection of particles and radiation with a resolution of at least 100 μm. It consists of a planar array of spherical granules for which the spread in transition temperatures is an order of magnitude smaller than that of the colloidal device. Positional sensitivity (in one dimension) is achieved by analyzing the amplitudes of the signals from two SQUID pick-up coils and therefore only a few channels of electronics are required. The narrow spread in the size and positional ordering of the granules reduces the distribution of signal amplitudes originating from individual grains thereby allowing the dependence of signal amplitude on the distance from the coils to be utilized as signature of position.

Avalanche effect in the planar array of superheated superconductors

An avalanche effect has been observed in a cryogenic detector based on the planar array of superheated superconductors (PASS). The indium PASS, fabricated by photolithography on a mylar substrate, consisted of 40 well-separated lines each containing about 175 spheres of diameter 18 μm and separation 20 μm with those at the end being shielded by superconducting wire. The magnetic field was applied in the PASS plane parallel to the lines. Avalanche events in which several granules changed their state from superconducting to normal were triggered by the nucleation of the transition in a single grain by an α-particle.