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Bunch Purity

Fill pattern diagnostics in synchrotron rings

Operating a synchrotron ring as a dedicated user facility demands to characterize the temporal shape of the electron bunches, the so-called "fill pattern". This is important for several reasons, including checking the quality of the injection system and the generation of special fill patterns for time-resolved experiments. The bunch purity is defined as the relative intensity ratio of the unwanted satellite bunches with respect to the main bunches.

Typicalsetup for bunch purity measurementsTime-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.

Typicalsetup for bunch purity measurementsPicoQuant 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 phython software to integrate the PicoHarp 300 into the Tango Control Software used at the ALBA Synchrotron is also being developed.

TCSPC units

PicoHarp300 - time tagging unitPicoHarp 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 time tagging moduleHydraHarp 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

TimeHarp260 - time tagging moduleTimeHarp 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 - Hybrid Photomultiplier Detector Assembly 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 AssemblyPMA 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

Tau-SPAD - single photon sensitive detectorτ-SPAD

Single Photon Counting Module

  • Timing resolution down to <350 ps (FWHM)
  • Detection efficiency up to 70%
  • Very low dark counts
  • NIM and TTL signal output

PDM SPAD - single photon sensitive detectorPDM 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.

Latest 10 publications related to Bunch purity

The following list is an extract of 10 recent publications from our bibliography that either bear reference or are releated to this application and our products in some way. Do you miss your publication? If yes, we will be happy to include it in our bibliography. Please send an e-mail to info@picoquant.com containing the appropriate citation. Thank you very much in advance for your kind co-operation.