Experience with CAEN counter

1
Experience with CAEN counter timer module

• Ljubljana, March 2008
• Dušan Ponikvar, Dejan Paradiž

2
Present state

• We have connected CAEN V1290N counter-timer
  module with CAEN V1718 USB-VME interface and can
  control both units using Linux based PC
• We have prepared the software in C for reading
  and evaluation of results
• We have tested the setup using high stability
  generators and GPS based 1PPS

3
DT for periodic pulses
DT ps
100ps
Sample number

• Input is 20000 Hz from Agilent function generator
  HP33250
• Jitter specifications (rms) 100ppm 50ps 5ns
• CAEN 1290N internal clock of 40MHz used
• Measurement duration 1s
• Deviation /- 125ps

4
DT for 1pps pulses from HP33250
DT ps
50ns
Sample number

• Input is 1 Hz from Agilent function generator
  HP33250
• Jitter specifications (rms) 100ppm 50ps
  100ms
• CAEN 1290N internal clock of 40MHz used
• Measurement duration 2 hours
• Deviation /- 50ns

5
DT for 1pps pulses from GPS
DT ps
50ns
Sample number

• Input is 1PPS from GPS
• Jitter specifications (max) /- 150ns
• CAEN 1290N internal clock of 40MHz used
• Measurement duration 1,5 hours
• Deviation /- 100ns after initial warming-up
  period

6
Hardware
GPS1pps
Photonpulses
RS232

• Signal sources
• CAEN inputs are connected to signal sources using
  home-made TTL to NIM translator
• PC is a Linux based machine, disk HD is an
  integral part of the PC

SYNC 20kHz
USB-VMECAEN 1718
COUNTERCAEN 1290
TTL-NIMHOME
PC
HD
7
CAEN V1290N
Counter state
21
2 -1
0
t

• V1290N uses 21 bit counter, clock frequency is
  40MHz counter period equals 52ms
• Continuous storage mode is used
• Result is the state of the counter at the arrival
  time of the electrical pulse 5 bit identifier
  (00000) 5 bit channel number 21 bit counter
• Results are grouped in CAEN internal buffer and
  periodically transferred to PC using USB bulk
  transfer

8
CAEN V1290N

• Periodic synchronization pulses are applied to
  V1290N spare input to identify counter periods
• Frequency must be at least 20kHz
• Lots of sync pulses!
• What we expect to count is - few thousands (up
  to 10k) pps photon pulses, - 20k sync
  pulses and - 1PPS from GPS
  --------------------------------------------------
  --------------- our counting system can
  cope with it

9
PC

• Linux based PC is used to collect measurement
  results and store them to disk
• Maximum throughput of the system is about 100.000
  pulses per second when our software is running at
  high priority
• File size is 100MB maximum, therefore results of
  the measurement must be stored in several
  consecutive files
• PC hardware specifications AMD Athlon(tm) XP
  1700, 512MB memory

10
Software

• The software consists of two parts
• Data from CAEN to disk on-line data streaming
• Data from disk to evaluation of-line evaluation

PC
CAEN
HD
PC
HD
USER
11
Hardware built

• CAEN 1290N requires NIM standard inputs a 4
  channel TTL to NIM translator was built, since
  this was faster than buying it
• CAEN 1290N requires positive differential ECL
  inputs for sync clock of 40MHz a logic level
  translator was built for the same reason

12
Immediate plans

• We currently have some problems with the GPS 1PPS
  output antenna? Old GPS? Warming?
• We need to introduce 1PPS sync pulses into CAEN
  1290N no problem
• We need to include RS232 output from GPS (time
  stamp) into streamed file with CAEN 1290N
  measurement results to identify absolute time
  no problem
• Testing with better clock and GPS system