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A high speed, wide dynamic range digitizer circuit for photomultiplier tubes

Technical Report ·
DOI:https://doi.org/10.2172/10167137· OSTI ID:10167137
; ; ; ; ; ;  [1];  [2]
  1. Fermi National Accelerator Lab., Batavia, IL (United States)
  2. Univ. of California, Los Angeles, CA (United States). Physics Dept.
High energy physics experiments running at high interaction rates frequently require long record lengths for determining a level 1 trigger. The easiest way to provide a long event record is by digital means. In applications requiring wide dynamic range, however, digitization of an analog signal to obtain the digital record has been impossible due to lack of high speed, wide range FADCs. One such application is the readout of thousands of photomultiplier tubes in fixed target and colliding beam experiment calorimeters. A circuit has been designed for digitizing PMT signals over a wide dynamic range (17--18 bits) with 8 bits of resolution at rates up to 53 MHz. Output from the circuit is in a floating point format with a 4 bit exponent and an 8 bit mantissa. The heart of the circuit is a full custom integrated circuit called the QIE (Charge Integrator and Encoder). The design of the QIE and associated circuitry reported here permits operation over a 17 bit dynamic range. Tests of the circuit with a PMT input and a pulsed laser have provided respectable results with little off line correction. Performance of the circuit for demanding applications can be significantly enhanced with additional off line correction. Circuit design, packaging issues, and test results of a multirange device are presented for the first time.
Research Organization:
Fermi National Accelerator Lab., Batavia, IL (United States)
Sponsoring Organization:
USDOE, Washington, DC (United States)
DOE Contract Number:
AC02-76CH03000
OSTI ID:
10167137
Report Number(s):
FNAL-TM--1895; CONF-9405168--3; ON: DE94015187
Country of Publication:
United States
Language:
English