Libera BLM

The Libera BLM is a processor for signals coming from the beam-loss detectors. In contrast to other similar BLM systems, it detects losses ranging from a single electron to the huge losses that usually occur during injection. Thanks to its high time resolution (8 ns) and 50 Ohm input termination, it provides detailed insight into sub-turn and intra-pulse losses. When switched to a high-impedance input termination, it is able to detect very small losses.

The instrument connects to up to four beam-loss detectors and provides them with power and gain-control voltage.

Product Description


  • Portable system, easy to deploy and use
  • Compact and robust design
  • Power over Ethernet for complete system
  • Re-configurable processing scheme
  • No maintenance required
  • Variety of interfaces (e.g. EPICS, TANGO, HTTP, MATLAB, etc.)

Data processing:

The signal from the beam loss detector (usually a photo-multiplier tube) is typically a unipolar pulse or train of pulses with negative polarity. Example of a loss signal is shown in the figure below.

Processing is split to 2 general principles:

  • buffered mode
  • counting mode

Data from both modes can be used in parallel.

In the buffered mode, the raw sampled data is stored in a buffer upon a trigger event (auto-trigger or external). Digital signal processing includes DC offset removal, integration/averaging interval and ADC mask which is applied to raw ADC samples. Decimated data is stored in the SUM and AVG buffers and streamed to a continuous SA data stream according to figure below.

In the counting mode, the raw sampled data is continuously (8 ns) monitored for the various absolute or relative thresholds. When the A/D converter is locked to a reference clock, it is possible to adjust up to two configurable detection windows that monitor only a selected part of the fill pattern. Outputs are 2 counter streams according to figure below.

With up to 4 beam loss detectors connected to the same instrument, an algorithm can automatically detect if the loss was detected in all detectors within the same time window. This is called coincidence counting mode. Coincidence is counted for each of the 4 channels resulting in 4 coincidence counting data streams. Configuration logic (example for master channel A) is shown in figure below.


  1. Memory card slot.
  2. Serial console (Micro-B USB).
  3. RJ-45 for 1000Base-T Cu GbE connection and Power-over-Ethernet.
  4. USB slot.
  5. SMA connectors for connections to the beam loss detectors.
  6. LEMO coaxial, used for various trigger signals.
  7. RJ-25 6/6 for power supply and gain control for the beam loss detectors.

Set-up example:

Libera BLM provides the power and gain control voltage to up to 4 beam loss detectors via standard flat cable (6 wires). High voltage is generated inside the photo-multiplier tube (PMT). Output signal from the PMT to the Libera BLM is provided through a standard 50 Ohm coaxial cable.

Beam loss detector must be exposed to the electromagnetic shower. The scintillator is located in the upper part of the detector, about 11 cm from top. Orientation of the detector with reference to the vacuum chamber shall be decided after tests. Typically, it is positioned vertically  or horizontally and fitted to the vacuum chamber directly.

The Libera BLM is installed outside the tunnel. Cable lengths for the beam loss detectors can range up to 100 meters (tested).

Hardware capabilities and specifications of Libera BLM
Libera BLM
General product codeLBLM
Input channels4
Input frequency range~35 MHz large signal bandwidth
~50 MHz small signal bandwidth
Matching impedance50 Ohm / 1 MOhm, software selectable
Maximum input signal+/- 5 V @ 50 Ohm
+/- 1.25 V @ 1 MOhm
A/D conversion125 MHz, 14 bit
Power supplyPower-over-Ethernet (<15 W)
Timing signalsElectrical, 3 inputs
Output channels4x power supply (up to +/-15 V)
4x gain control (up to +12 V)
Specifications of Libera BLD
Beam Loss Detector (BLD)
General product codeLBLD
Beam loss detectorOutside dimensions (H x W x D) mm: approximately 220 x 25 x 25 (without the fitting holder)
Weight: approximately 150 g (without the lead cover)
Operating temperature: +10°C to +40°C
Scintillator rodMaterial type: EJ-200 from Scionix, gamma-ray detection
Length: 100 mm Diameter: ~22 mm
PhotosensorHamamatsu 10721-110
Supply voltage: (5+/-0.5) V
Input current: 2.7 mA maximum
Gain control voltage: 1.1 V maximum
Rise time: 0.57 ns
Dark current: 1 nA (typical)
Peak sensitivity wavelength: 400 nm
Dimensions (H x W x D) mm: 50 x 22 x 22
Typical applications
Low loss detectionDetecting volumes as low as a single electron loss using high input impedance and high gain.
Strong and fast loss detectionDetecting strong losses during injection (typically).
Automatic loss detectionAdjustable threshold for automatic buffer storage.
Configurable processing parametersADC offset compensation, integration and averaging window lengths, less detection windows and individual channel delays.
Counting modesSelect between static and dynamic thresholds for loss counts. Apply a custom recovery time and threshold.
Coincidence loss detectionCompare up to 4 channels for simultaneous loss events.
Loss value calibrationCompensate the raw loss value with current gain settings (attenuation, photosensor dynamic gain and photosensor static gain).
Postmortem data storageDedicated memory buffer is intended for storing the data just before a postmortem trigger event.
Photosensor controlProvide power supply and adjust gain control voltage to up to 4 independent channels.
User Interfaces

The instrument runs on a Libera BASE software infrastructure. The infrastructure supports various plugins (interface servers) that are compatible with most common control system interfaces on users’ side:

  • EPICS: libera-ioc
  • TANGO: libera-ds
  • MATLAB/LabVIEW: libera-telnet-server
  • HTTP/WEB: libera-http-plugin
  • C++ : libera-mci
  • PYTHON: libera-pymci

Graphical user interface for TANGO users is built by the AtkPanel tool automatically. EPICS users have various options: from EDM, caQtDM to CSS.

As an example, the gallery below shows the GUI panels built on the EDM technology.

Libera BLM
Clear filters
Optimized Beam Loss Monitor System For The ESRF
Prototype results with a complete Beam Loss Monitor System optimized for synchrotron light sources (IPAC’15, Richmond, VA, USA)

Libera BLM is used at the following labs:

  • The European Synchrotron Radiation Facility – ESRF (France)
  • Deutsches Elektronen-Synchrotron (DESY) – PETRA III (Germany)
  • National Synchrotron Radiation Research Center (NSRRC) – TPS, TLS (Taiwan)
  • Synchrotron Light Research Institute – SLRI (Thailand)
  • The Synchrotron-Light for Experimental Science and Applications in the Middle East (SESAME) – SESAME (Jordan)
  • SACLA – Spring-8 (Japan)
  • Diamond Light Source (United Kingdom)
  • Pohang Accelerator Laboratory (PAL) – PLS II, XFEL ITF (South Korea)
  • Hiroshima Synchrotron Radiation Center – HiSOR (Japan)
  • Cornell University – CHESS (United States)