Time stamping with CAEN V1290N Bled, 26 th – 28 th March 2008 Dušan Ponikvar, Dejan Paradiž Faculty of Mathematics and Physics Ljubljana, Slovenia

Present state We have connected CAEN V1290N time-tag 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

 T for periodic pulses Input is Hz from Agilent function generator HP33250 Jitter specifications (rms): 100ppm + 50ps = 5ns CAEN 1290N internal clock of 40MHz used Measurement duration: 1s Deviation: +/- 125ps  T [ps] Sample number 100ps

 T for 1pps pulses from HP33250 Input is 1 Hz from Agilent function generator HP33250 Jitter specifications (rms): 100ppm + 50ps = 100  s CAEN 1290N internal clock of 40MHz used Measurement duration: 2 hours Deviation: +/- 50ns  T [ps] Sample number 50ns

 T for 1pps pulses from GPS 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 Sample number  T [ps] 50ns

Hardware 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 PC HD GPS 1pps “Photon” pulses USB-VME CAEN 1718 COUNTER CAEN 1290 TTL-NIM HOME SYNC 20kHz RS232

The software consists of two parts: 1. Data from CAEN to disk: on-line data streaming 2. Data from disk to evaluation: of-line evaluation Software PCCAEN HD PC USER HD

CAEN V1290N V1290N uses 21 bit counter, clock frequency is 40MHz: counter period equals 52  s 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 time-tag Results are grouped in CAEN internal buffer and periodically transferred to PC using USB bulk transfer Counter state t

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 time-tag is: - few thousands (up to 10k) pps “photon” pulses, - 20k sync pulses and - 1PPS from GPS our system can cope with it

PC Linux based PC is used to collect measurement results and store them to disk Maximum throughput of the system is about 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

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

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