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Appendix E. EPD File Structure (continued)

5. LEMMS PHA Block

Source: T. P. Armstrong, April 1985

The LEMMS PHA data are acquired in a cycle of 91 SCLK counts (91 packets of 2/3 second in length). During this 60 2/3 second interval 11 spectra from the A detector, one from E and one from F are acquired. Each spectrum consists of 47 energy channels accumulated in 2/3 of a second (12 degrees of rotation at the nominal spin rate). The shortest logical record interval for this data is 60 2/3 seconds. A logical record will consist of a variable number of physical records. There will be three records in the format listed below for each step position which occurs in this time interval. The groups of three records will have LEMMS data from Detectors A, E, and F. If all possible motor positions were present in the interval, there would be 24 physical records per logical record interval. Each physical record has approximately 12 k bytes.

1Spin rate at start1 4-byte real
2Spin rate at end1 4-byte real
3Number of spins in this average1 4-byte real
4Number of full sectors1 4-byte integer
5Step position of this record1 4-byte integer
6Detector flag: 0="fill," 1=A, 2=E, 3=F1 4-byte integer
7 PHA(47,32) Detector A, E, or F Pulse Height Spectrum
Units:Counts per second
Type:4 byte real numbers
First Index:Energy bin from 1 through 47
Second Index: 32 repetitions to cover the 30 possible sectors of a spin 
8 IPHADQ(47,32) Data presence and quality flag for item 6
Type:2 byte integers
Contents: Bit 0-7 Unsigned integer no. of samples
 8 spare
 9 spare
 10 spare
 11 spare
 12 spare
 13 spare
 14 spare
 15 data presence, 1=yes, 0=no
9 RA30(9,33) Count rates for detector A, E, or F
Type:4 byte real numbers
First Index: Channel
1. A0 E0 F0
2. A1 E1 F1
3. A2 E2 F2
4. A3 E3 F3
5. A4 EB1 FB1
6. A5 EB2 FB2
7. A6 spare spare
8. A7 spare spare
Second Index:1 thru 32 is synchronous accumulation corresponding to LEMMS PHA spectrum
10 IDQ(9,33) Data presence/quality flags
Type:2 byte integer
Contents: Byte 2  
  0000 Data missing (not on EDR)
  0010 Data missing (wrong subcom pos.)
  0100 Data invalid (motor movement)
  0110 Data invalid (exceed max. rate)
  1000 Data invalid (discontinuity)
  1010 Data invalid (spare)
  1100 Data invalid (spare)
  1110 Data invalid (spare)
  0001 Data valid (nominal)
  0011 Data valid (high threshold)
 0101 Data valid (autocal. fault)
 0111 Data valid (spare)
 1001 Data valid (spare)
 1011 Data valid (spare)
 1101 Data valid (spare)
 1111 Data valid (spare)
 Byte 1 Unsigned integer # of samples in this average

Next: 6. Rate Calc Block

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Updated 10/12/04, T. Hunt-Ward