Bunch Purity

Time-Correlated Single Photon Counting (TCSPC) is one of the most commonly used methods to measure the bunch purity. Using TCSPC, the arrival time of single photons is measured, which are emitted by the electron bunches as they pass through a particular dipole in the storage ring. The photons are typically detected using, for example, a MCP-PMT for the visible photons, and an APD for the X-ray photons. The time difference of the single photon signal with respect to the clock pulse synchronized to the rf signal of the storage ring is processed by the TCSPC unit, and the histogram of the photon arrival time is accumulated, which represents the bunch filling pattern.

PicoQuant TCSPC modules are very well suited for fill pattern diagnostics in synchrotron light sources. As opposed to conventional TCSPC systems that have a very limited TAC range, both units provides 65535 histogram channels and allow to cover large time spans at high temporal resolutions.

The PicoHarp 300 is, e.g., currently used for fill pattern diagnostics at:

• Bessy II (Berlin, Germany) - live measurement results available
• Swiss Light Source (Villigen, Switzerland)
• Diamond Light Source (Chilton, UK)
• Australian Synchrotron (Clayton, Australia)
• Taiwan Light Source (Hsinchu, Taiwan)
• ALBA Synchrotron (Barcelona, Spain)
• SLAC (Menlo Park, CA, USA)

In collaboration with BESSY II PicoQuant is also offering a free LabVIEW Software for the PicoHarp 300 acting as an EPICS Server for fill pattern monitoring. Please contact us for further details.
A python software to integrate the PicoHarp 300 into the Tango Control Software used at the ALBA Synchrotron is also being developed.

TCSPC units

MultiHarp 150

High-Throughput Multichannel Event Timer & TCSPC Unit

• 4, 8, or 16 independent input channels and common sync channel (up to 1.2 GHz)
• High sustained data throughput (80 Mcps in time tagging mode, 180 Mcps in histogramming mode)
• Record-breaking dead time (650 ps) per channel
• No dead time across channels

PicoHarp 300

Compact Dual-Channel Picosecond Event Timer

• Two identical synchronized but independent input channels
• 65536 histogram time bins, minimum width 4 ps
• Histogrammer measurement range from 260 ns to 33 µs (depending on resolution)
• USB 2.0 connection

HydraHarp 400

Multichannel Picosecond Event Timer

• Up to 8 independent input channels and common synch channel (up to 150 MHz)
• 65536 histogram bins per channel, minimum width 1 ps
• Histogrammer measurement ranges from 65 ns to 2.19 s
• USB 3.0 interface

TimeHarp 260

TCSPC and MCS board with PCIe interface

• One or two independent input channels and common synch channel (up to 84 MHz)
• Two models with either 25 ps (PICO model) or 1 ns (NANO model) base resolution
• "Long range mode" option for PICO model with 2.5 ns base resolution
• Ultra short dead time (<25 ns for PICO model, <1 ns for NANO model)

Photon Counting Detectors

PMA Hybrid Series

Hybrid Photomultiplier Detector Assembly

• Timing resolution down to <50 ps (FWHM, cathode dependent)
• Detection efficiency up to 45 % at 500 nm (cathode dependent)
• Active area up to 6 mm
• Negligible afterpulsing

PMA Series

Photomultiplier Detector Assembly

• Timing resolution < 180 ps (FWHM)
• Quantum efficiencies up to 40% (cathode dependent)
• Spectral ranges from 185 nm to 900 nm available
• Optional thermoelectric cooler

PDM Series

Single Photon Avalanche Diodes

• Timing resolution down to <50 ps (FWHM)
• Detection efficiency up to 49%
• Different active areas: 20, 50 and 100 µm
• Ultra stable at high count rates

Bunch purity measurements at BESSY II

Section of the regular BESSY II multibunch fill pattern recorded with the PicoHarp 300 using a time bin witdh of 64 ps.

Data collection: courtesy of Karsten Holldack, Bessy II, Germany.