Multi-channel integrated circuit

Details Multi-channel integrated circuit Multi-channel integrated circuit

2002-10-24

2004-04-13

Le, Dinh T. (Department: 2816)

Miscellaneous active electrical nonlinear devices, circuits, and

Signal converting, shaping, or generating

Slope control of leading or trailing edge of rectangular or...

C327S051000, C327S069000

Reexamination Certificate

active

06720812

ABSTRACT:

GOVERNMENT RIGHTS NOTICE
There are no government rights on this patent application.
FIELD OF THE INVENTION
There is need for high spatial and energy resolution x-ray, gamma ray and particle detectors. Scintillation counters read out by individual photomultiplier tubes has limitations in both spatial and energy resolution. Therefore, there is need for high resolution imaging solid state sensors, as increasingly sophisticated and higher resolution detectors are needed. These new imaging sensors with large number of channels require monolithic, compact, low noise and multi-channel integrated circuits for reading out the sensors. The integrated circuit needs to be capable of matching the energy resolution coming from the detectors. A new low noise multi-channel integrated circuit has been developed which can read out high-resolution, position-sensitive sensor arrays. The developed integrated circuit has low noise, an accurate timing output and a wide dynamic range. The new integrated circuit can be used in astrophysics, nuclear medicine and physics, radiography, security, medical and industrial imaging.
The technical viability of this approach has already been demonstrated by NOVA R&D, Inc., through its current RENA (Readout Electronics for Nuclear Application) chip which has been used successfully with CdZnTe (CZT), CdTe, GaAs, Si, and Si(Li) detectors as well as gas microstrip detectors. The new ASIC is called RENA-
2
and it is a major advancement over RENA.
The demand for high-performance integrated, multichannel front-end and readout electronics is commensurate with the increasingly stringent detection requirements of many NASA missions and experiments. Important instrumentation segments that the developed ASIC hopes to serve are those of advanced hard x-ray and gamma-ray telescopes and x-ray and gamma ray astrophysics in general. Certain experiments in cosmic ray astrophysics would also benefit from specific design features of the new ASIC (Application Specific Integrated Circuit).
This ASIC can be used in NASA missions such as the planned Advanced Compton Telescope (ACT), a high-priority space-based instrument, is intended to achieve significantly enhanced sensitivities for gamma rays in the 200 keV-30 MeV range. Others are the Minute-of-Arc Resolution Gamma Imaging Experiment (MARGIE) and the Energetic X-ray Imaging Survey Telescope (EXIST).
The versatile RENA-
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ASIC with wide range of features can help in advancing the present knowledge of the fluxes of energetic charged particles in space and their production mechanisms and understanding the ways in which these particles are energized and transported throughout the universe. This is fundamentally important for understanding how the cosmos functions. The new ASIC will both enable and enhance new investigations of energetic charged particles by NASA's science missions. Instruments incorporating the RENA-
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chip will be much less resource-intensive than their present-day predecessors. Replacement of the usual many strings of charge amplifier circuitry with a single chip saves volume, weight, and power. New missions, such as the miniaturized spacecraft being planned, will be greatly enhanced in their ability to measure energetic particles by RENA-
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. Instruments with superior measurement capabilities will also be enabled. The new chip will allow a new generation of space flight instruments to have a large impact on imaging and understanding of x-rays, gamma rays and energetic charged particle fluxes in space.
The new chip discussed in this report can also be used for many other applications such as nuclear physics; nuclear chemistry; nuclear medicine; medical and industrial radiography; x-ray and gamma ray imaging; nondestructive evaluation (NDE) and nondestructive inspection (NDI) applications; and baggage, container, vehicle, mail, etc. scanning for security and other reasons. Medical imaging applications include high resolution solid state gamma camera and Single Photon Emission Computed Tomography (SPECT) based on the solid state gamma camera concept. Other medical imaging applications include small compact gamma camera and SPECT for small organ imaging such as breast and thyroid and/or metabolic imaging of small animals. Industrial applications include mainly NDE and NDI. Security applications include high resolution baggage, container and vehicle imaging.
BACKGROUND OF THE INVENTION
Over the past few years, solid state detectors such as silicon strip detectors have revolutionized high energy and nuclear physics research. The progress and demand for silicon strip detectors also increased in other fields where their potential high resolution detection capability became apparent. Although an excellent detector, silicon, with an atomic number (Z) of 14, does not have good quantum efficiency for higher energy x-rays and gamma rays. Therefore, recently a significant amount of research has been carried out to develop high-Z strip and pixel detectors. Out of this work, six detector materials have become the potential front runners, Germanium (needs cryogenic cooling), CdZnTe, CdTe, HgI
2
and GaAs (both can be used at or near room temperature). A newcomer to the field, with very high Z, is PbI
2
. These materials provide high detection efficiency for x-ray energies in the 10 to 1,000 keV range with detector thickness of about 0.5 to 15 mm. One positive effect of this small thickness is that depth effects, which degrade position resolution for radiation coming in at an angle, are minimized. Consequently, these high-Z detectors are now routinely manufactured with strip or pixel sizes in the mm to sub-mm-range. Such high spatial and energy resolution two-dimensional x-ray and gamma ray sensors are expected to become the standard in the future.
Although strongly promising high-Z position sensitive solid state detectors were developed, an essential component to make them viable instruments for detecting and imaging x-rays, gamma rays and particles has been missing. Such detectors have many channels with small pitch, and reading them out with conventional discrete or hybrid electronics is not a viable option. These detectors require monolithic multichannel readout electronics to handle both the high number of channels and small pitch. Such ASIC chips, e.g., the Amplex (CERN) and SVX (LBNL) chips, have been developed for accelerator-based high energy physics experiments. However, these chips lack two major functions, which are not needed for those experiments but render the chips mostly unsuitable for use in nuclear physics, astrophysics, and medical and industrial imaging:
1. They do not have a self trigger output. In high energy physics experiments, an external machine trigger is available to inform the data acquisition (DAQ) system about the exact time of an event for reading out the chips. In addition, the event trigger is typically based on the overall event topology rather than the signal levels in individual channels, which precludes its implementation on the readout chip.
2. The solid-state detectors for which these ASICs were developed provide position information only; the energy information is largely irrelevant as the particles of interest are all minimum ionizing anyway. Consequently, such chips do not need to have low noise and thus high energy resolution capability.
By contrast, in space-based (high-energy) astrophysics as well as most medical and industrial imaging, the x-ray and gamma-ray photons and charged particles come randomly. In many applications, it is also important to measure the x-ray, gamma ray and particle energies with as high accuracy as possible. Therefore, the application of position sensitive solid state detectors to nuclear and astrophysics and to medical and industrial imaging was largely delayed as a suitable ASIC readout chip was not available. There have only been few exceptions such as the ACE chip used with silicon strip detectors on board the Advanced Composition Explorer (ACE) space mission. It is thus important to develop versatile ASICs for reading out solid state sensors for ap

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