An analysis is presented of signal, noise and position resolution relations for some of the most interesting position-sensing methods. "Electronic cooling" of delay line terminations is introduced in order to reduce noise in the position-sensing with delay lines. A new method for terminating transmission lines and for "noiseless" damping which employs a capacitance in feedback is presented. It is shown that the position resolution for the charge division method with resistive electrodes is determined only by the electrode capacitance and not by the electrode resistance, if optimum filtering is used.

Signal, Noise and Resolution in Position-Sensitive Detectors

A position sensitive proportional counter is described which shows some novel features in the method of position encoding compared with previous systems. The encoding is done by an inductance‐capacity (L‐C) line connected to cathode strips, rather than by resistance‐capacity encoding (high resistance) using the anode wire. The spatial resolution for a counter length of 8 cm is 0.2 mm (which corresponds to 0.01° for the geometry used here). Counting can be at high rates for indefinite periods.

Position sensitive x‐ray detector

Gap junction structures. V. Structural chemistry inferred from X-ray diffraction measurements on sucrose accessibility and trypsin susceptibility.

A versatile photon and charged particle imaging system is described. The Ranicon employs a microchannel electron multiplier plate to convert each detected event into a charge signal. This charge pulse is proximity-focused onto a large-area resistive anode plate equipped with pickup electrodes on its edges. Each event is located electronically by the ratios of the charges collected at the edges or by the differences of the signals' risetimes. One- or two-dimensional pictures are built up by storing events digitally (e.g., a core memory) or in analog form (e.g., a storage oscilloscope). Compact laboratory models have been constructed and tested. Operating characteristics, applications, limitations, and advantages of the Ranicon are discussed.

The Ranicon: A resistive anode image converter

Detailed measurements, line identifications, and modeling calculations of the Fe XVII L-shell emission spectrum between 9.8 and 17.5 A are presented. The measurements were carried out on an electron beam ion trap under precisely controlled conditions where electron-impact excitation followed by radiative cascades is the dominant line formation process. In addition to the strong transitions emanating from the n = 3 shell, we identify and accurately determine wavelengths for transitions from higher shells up to n = 11, including two electric quadrupole transitions that have not been previously identified. Various theoretical values, including new distorted wave calculations, are compared to our measurements, which establish definitive values for testing spectral modeling predictions. We find a value of 3.04 ± 0.12 for the ratio of the intensity of the 2p-3d1P1 resonance and of the 2p-3d3D1 intercombination line situated at 15.01 and 15.26 A, respectively. This value is higher than the values observed in solar spectra, which supports claims that the solar value is affected by resonant scattering. However, because our value is significantly lower than calculated values, the amount of scattering has probably been overestimated in past analyses. Comparisons of the measured intensity ratios of the transitions originating in levels of higher principal quantum number n with present distorted wave calculations show good agreement up to n = 6. The combined flux of all 2p-nd transitions with n ≥ 5 and all 2s-np transitions with n = 4 and 5 relative to the flux of the 15.01 A resonance line has been measured to be 0.13+ 0.04−0.03 .

https://iopscience.iop.org/article/10.1086/305941/pdf

Laboratory Measurements and Modeling of the Fe XVII X-Ray Spectrum

A new method was developed for determining the position of ionizing events by measuring the risetime of output pulses from detectors having high resistance collectors. Several prototype detectors, such as proportional counters, pulse ion chambers, and surface barrier detectors, were constructed and tested for this purpose. These detectors were treated as infinite RC lines with distributed parameters, and the position‐dependent risetime of the output pulses was measured by crossover timing after double RC differentiation. With these detectors the impact locations of x rays, thermal neutrons, and alpha particles were determined. The spatial uncertainty obtained with 400 mm long proportional counters was 0.5 mm FWHM, for 22 keV x rays, 6 mm FWHM for thermal neutrons, and 0.66 mm FWHM for 242Cm alpha particles. A spatial uncertainty of 1.25 mm FWHM was obtained with a pulse ion chamber for 242Cm alpha particles. This method of determining the position of an ionizing event gives good linearity and spatial reso...

C. J. Borkowski

Papers

New Type of Position‐Sensitive Detectors of Ionizing Radiation Using Risetime Measurement