Lloyd B. Robinson

A high-speed 4096-channel analogue-digital converter for pulse height analysis

Abstract A 12-bit analogue-digital converter of the successive binary approximation type is described. The unit accepts input pulses less than 1 μsec long and produces a 12-bit digital output in a register in less than 25 μsec. Use of the random pedestal technique described by Gatti 1 ) and careful design results in essentially equal channel widths from channel 40 to 4000. Integrated circuits are used for all digital operations, producing a compact unit despite the circuit complexity of the successive approximation technique. The unit is designed for convenient linking to a computer using either its program interrupt or direct memory access facilities, but can be operated equally well with any memory unit.

An analog store and multiplexer for pulse-height analysis

Abstract The report describes an electronic analog pulse storage unit. Used in conjunction with on-line computers, the unit allows high-resolution pulse-height analysis of eight-parameter coincidence events by use of a single ADC.

An inexpensive gain stabilizer controlled by a time-shared computer☆

Abstract An electronic pulse amplifier is described for automatic gain correction in high-resolution high-rate pulse-height analysis systems. The circuit gain is controlled by a PDP-7 computer devoting less than 4 ms per second of its time to provide gain correction signals for up to 8 ampliers. Necessary control voltages are developed in the computers CRT display circuits and transferred to a “sample and hold” circuit associated with each gain stabilizer. Gain control is accomplished by adjusting the gate voltage of an FET which shunts a small fraction of the total signal.

SEMI-CONDUCTOR PROBE FOR INVESTIGATING ACCELERATOR BEAM PULSES

Abstract An instrument which makes possible the investigation of individual beam pulses from a cyclotron is described. It utilizes a fully depleted diffused-silicon junction detector of 100–200 microns thickness. The detector characteristics of fast charge collection time (∼1 ns) and of inherent amplification are important in this application. Examples of the detector system response to beams from the Berkeley sector-focused cyclotron are presented.

Packaging design for Lawrence Berkeley National Laboratory high-resistivity CCDs

The Lawrence Berkeley National Laboratory has been developing fully-depleted high resistivity CCDs. These CCDs exhibit very high red quantum efficiency, no red fringing, and very low lateral charge diffusion, making them good candidates for astronomical applications that require better red response or better point spread function than can typically be achieved with standard thinned CCDs. For the LBNL 2Kx4K CCD we have developed a four-side mosaic package fabricated from aluminum nitride. Our objectives have been to achieve a flatness of less than 10 micrometers peak-to-valley and a consistent final package thickness variation of 10 micrometers or less in a light-weight package. We have achieved the flatness objective, and we are working toward the thickness variation objective.

A time derandomizer for analog pulses

Abstract A storage unit for analog pulses is described which is used to decrease counting losses in high-rate, high-resolution, pulse-height analysis experiments. Three pulse stretchers connected in series store up to three pulses until they can be processed by an external analog-to-digital converter. An effective dead time of 6 μs is achieved when analyzing randomly occuring pulses at rates up to 20 000 cps. No degradation in pulse height resolution due to the insertion of this instrument has been detected.

Applications of Small Computers in Nuclear Spectroscopy

Two data-acquisition systems are described; both are built around small digital computers and are designed for use in nuclear spectroscopy experiments. The computers are used for storage of data, graph plotting, control of hardware devices and CRT displays, and for routine arithmetical operations required in the preliminary analysis of experimental data. Both computer systems can be easily operated by relatively inexperienced personnel. Most routine operations can be controlled with simple multiposition selector switches, although more specialized operations are carried out with a question-and-answer routine on the typewriter. Operations involving CRT display can be initiated with the light pen. With this procedure, routine operation of the computer requires little more training than is needed to operate a pulse-height analyzer.

A VERSATILE SCALER AND READ-OUT SYSTEM

Abstract A scaling system is described whose automatic readout can record from an unlimited number of scalers or other digital equipment. The readout system normally controls a paper-type punch at 60 characters per second or a typewriter at 15 characters per second, but magnetic-tape output has also been used. The scaler has a dead time per count of less than 100 nsec. Nixietube display is provided and a wide range of operating modes are possible. Planar silicon transistors and diodes are used exclusively in both the scaler and the read-out.

The Lick Observatory charge-coupled device /CCD/ and controller

A flexible microprocessor-based controller for charge coupled device two-dimensional detectors is described. The controller can operate under manual control or as a slave to a remote computer linked by coaxial cable. The system is discussed along with data taken at the telescope and in the laboratory.

Indium-tin-oxide biased-gate technology

Ongoing experiments using thin electrically conducting transparent layers of Indium Tin Oxide to control the surface potential of thinned CCDs are described. The results are very encouraging with good uniform ultraviolet sensitivity being obtained from CCDs of different types and thinned by different processes. The enhanced response is stable in air and in vacuum for periods longer than a year. 2.