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Patrick Van Esch

Publications and source records attributed to Patrick Van Esch.

10 recordsLinked to original sources
arXiv2013

An Information-Theoretical Approach to Image Resolution Applied to Neutron Imaging Detectors based upon Individual Discriminator Signals

1D or 2D neutron imaging detectors with individual wire or strip readout using discriminators have the advantage of being able to treat several neutron impacts partially overlapping in time, hence reducing global dead time. A single neutron impact usually gives rise to several discriminator signals. In this paper, we introduce an information-theoretical definition of image resolution. Two point-like spots of neutron impacts with a given distance between them act as a source of information (each neutron hit belongs to one spot or the other), and the detector plus signal treatment is regarded as an imperfect communication channel that transmits this information. The maximal mutual information obtained from this channel as a function of the distance between the spots allows to define a calibration-independent measure of resolution. We then apply this measure to quantify the power of resolution of different algorithms treating these individual discriminator signals which can be implemented in firmware. The method is then applied to different detectors existing at the ILL. Center-of-gravity methods usually improve the resolution over best-wire algorithms which are the standard way of treating these signals.

physics.ins-det↗
arXiv2007

Multiple hits in wire chambers and other particle detectors

We propose an analysis of the dead time losses in counting imaging detectors such as MWPC which can resolve $k$ simultaneous hits, and analyze in more detail an $X-Y$ detector which has a third wire set which allows for the recognition of simultaneous impacts.

physics.ins-det↗
arXiv2006

Effects of ion drift on time-over-threshold charge estimates using first-order integrators in thermal neutron MWPC

Time-over-threshold measurements of the output of a first order integration amplifier can be used as a cheap way to estimate the charge deposited on a wire in an MWPC. Even if the time scale of the first order system is seemingly much larger than the signal development time, we noticed experimentally a significant deviation from the relationship of time-over-threshold and the charge, as would be naively expected from the exponential response of the amplifier. We strongly suspect the current induced by the residual ion movement to be at least partially responsible for this observation. It is of course well-known that the ion movement is responsible for the bulk of the signal generation in a wire chamber, this is not the point ; however, the surprise is rather that this movement has influences on time scales which are so long that the finite ion movement could be thought negligible. In this paper we will treat theoretically the influence of ion movement and of AC coupling on the expected time-over-threshold relationship and confront this to the measurements on a small test MWPC in thermal neutron detection.

physics.ins-det↗
arXiv2006

Design guide for electronics for resistive charge division in thermal neutron detection

An amplifier has been designed for optimal use of position sensitive thermal neutron detectors using the principle of resistive charge division. The important points in this optimization are: high counting rates and good spatial resolution. This amplifier is built as a hybrid circuit and is now used on several new instruments at the ILL. It consists of a fast low noise current pre-amplifier, a gaussian shaping circuit based on a 4th order active filter and an essentially noiseless baseline reconstruction. In this paper, we present a rather complete theoretical analysis of the problem that lead us to the choices made above, and allows for an optimal adaptation to other situations. An analysis of unwanted, secondary effects is also worked out.

physics.ins-det↗
arXiv2006

Off line Parallax Correction for Neutral Particle Gas Detectors

In a neutral particle gas detector, the parallax error resulting from the perpendicular projection on the detection plane or wire of the radial particle trajectories emanating from a point like source (such as a scattering sample) can significantly spoil the apparent angular resolution of the detector. However, as we will show, the information is not lost. We propose an off line data treatment to restore as much as possible the original scattering information in the case of a one-dimensional parallax effect. The reversibility of parallax follows from the algebraic structure of this effect, which is different from the resolution loss which is essentially irreversible. The interplay between finite resolution and parallax complicates the issue, but this can be resolved.

physics.ins-det↗
arXiv2006

An Electrostatic Lens to Reduce Parallax in Banana Gas Detectors

Cylindrical "banana" gas detectors are often used in fixed-target experiments, because they are free of parallax effects in the equatorial plane. However, there is a growing demand to increase the height of these detectors in order to be more efficient or to cover more solid angle, and hence a parallax effect starts to limit the resolution in that direction. In this paper we propose a hardware correction for this problem which reduces the parallax error thanks to an applied potential on the front window that makes the electrostatic field lines radially pointing to the interaction point at the entrance window. A detailed analytical analysis of the solution is also presented.

physics.ins-det↗
arXiv2006

An Optimal Lookup Table Construction for Charge Division with respect to Efficiency Flatness

Static lookup tables as often used in the position calculation electronics in position sensitive detectors suffer from the well known problem that the propagation of digitization errors in the division leads to unequal efficiencies for the different output channels. In this paper we present a solution to the construction of such a lookup table which is optimal in the sense that the least possible efficiency errors are committed in the class of monotone lookup tables. The obtained resolution is comparable to what is obtained using the standard implementation of the fixed point division. After a theoretical explanation, we present some experimental results confirming our claim.

physics.ins-det↗
arXiv2006

Capacity formulas in MWPC: some critical reflexions

An approximate analytical expression for "capacitance" of MWPC configurations circulates in the literature since decades and is copied over and over again. In this paper we will try to show that this formula corresponds to a physical quantity that is different from what it is usually thought to stand for.

physics.ins-det↗
arXiv2005

On the Everett programme and the Born rule

Proponents of the Everett interpretation of Quantum Theory have made efforts to show that to an observer in a branch, everything happens as if the projection postulate were true without postulating it. In this paper, we will indicate that it is only possible to deduce this rule if one introduces another postulate that is logically equivalent to introducing the projection postulate as an extra assumption. We do this by examining the consequences of changing the projection postulate into an alternative one, while keeping the unitary part of quantum theory, and indicate that this is a consistent (although strange) physical theory.

quant-ph↗