Merlin for Medipix3

26 August, 2013
/ Comments Off on Merlin for Medipix3
/ By QD

55um energy resolving detector with up to eight thresholds in colour mode, capable of 1200fps burst

The Merlin photon counting detector system with Medipix3 ASIC packs a lot in for its size.  With a vast range of applications, Merlin is a high performance X-Ray imaging detector that requires no additional cooling system and, being around the size of a mobile phone, is easily installed into small spaces. The system is supplied with a LabView GUI to get you up and running quickly while TANGO and EPICS drivers have been written to allow you to integrate it into your system.



  • Photon Counting Eliminating Dark Noise
  • Zero Dead Time Between Franmes
  • Spectroscopic Imaging
  • No External Cooling System
  • Compact Size
  • 55  μm
  • 1200 Frames Per Second
  • 1 μs Exposure Time
  • 5 – 17 keV Range
  • 12 and 24 Bit Counter Modes


Merlin is capable of  taking 1200 frames per second in burst mode and 100 frames per second in continuous mode. Allocated to each of its 55µm pixels are 2 x 12 bit counters which allows continuous read/write with no dead time between frames.  With 2 threshold levels per pixel, up to 8 thresholds can be set by creating a super-pixel (combining 4 pixels together).  Stepping through the resulting threshold images allows easy interpretation of the intensity of X-Ray absorption at user defined energy levels. Merlin is available with either a Single medipix3 chip (256×256) or Quad (512×512)  system and has excellent sensitivity in the 5-17 KeV range. The detector is already installed on 5 beamlines at Diamond Light Source and has had successful trials at other synchrotrons.




Coherent X-ray Diffraction

Bunch Synchronised Experiments


Surface Diffraction

Phase Contrast Imaging

Pump and probe experiments

Powder diffraction

Multi energy imaging

High speed real time imaging

Scanning Transmission Electron Microscope


The Merlin readout electronics are based on a National Instruments PXI FPGA system with some additional custom control electronics.  This is a robust, extensible and well supported platform with a long product lifetime.  It integrates an embedded high performance industrial grade PC and FPGA card with 512GB dedicated RAM.  The detector head is connected by a high density cable link that can be up to 10m long allowing a significant degree of flexibility in the mounting of the system.

As the Merlin contains an integrated PC, it requires no external input other than mains power to run.  In addition to its own intuitive graphical interface, the system also implements a TCP/IP based remote control function that allows easy integration with a users control systems.

What is Medipix 3RX

Medipix3 is a was developed by an international consortium including CERN, DESY, ESRF and Diamond and provides a range of features that are unavailable in other hybrid pixel detectors, including continuous read-write, colour mode, 12 or 24 bit mode selection and all in 55µm pixels. See the datasheet below or the paper for more details.


When a photon strikes near the edge of a pixel, the resulting charge may leak into neighbouring pixels by diffusion, sometimes below the threshold level.  In some detector systems this information is mis-interpreted as lower energy photons on the pixels.  Merlin is different and makes use of Medipix’s Charge Summing Mode.  Merlin recognizes that this information belongs to one event on one pixel rather than up to 4 weaker events on 4 pixels.  By reconstructing the event using the diffused charge data, Merlin ensures an accurate reading of the event giving improved results quality.

Merlin Datasheet


An example image from a Quad Merlin

An example image from a Quad Merlin

Q. How can Merlin be calibrated?
A. Your Merlin system comes pre-calibrated.  Should you wish to add more calibration points to a particular energy, this can be done through the LabView GUI and editing of a calibration text file.  Details on how to do this are in the Manual.

Q. Does Charge Summing Mode increase dead time?
A. Yes, very slightly since there is additional logic here.

Q. How long is the cable from the PC to the detector head?
A. Up to 10 meters.

Q. Is it possible to access the FPGA memory directly?
A. No, the system writes to local disk and/or TCP/IP link.


The following video shows a Quad Merlin (512 x 512 pixels, 28.2 x 28.2mm) recording a rotating chopper at a frame rate of 1KHz with no deadtime.

(We hear that this video doesn’t work on old versions of IE on Windows XP. For those affected might we suggest Chrome or Firefox).


  • Pixel Size 55 x 55 μm
  • Readout Time (continuous/12/24 bit) 0 μs / 850 μs / 1.8 μs
  • Maximum Frame Rate (burst / continuous) 1.2 kHz / 100 Hz
  • Dynamic Range 24 bit max
  • Maximum Trigger Response Jitter 20 ns
  • Threshold Range 5 keV upwards
  • Exposure Time minimum 1 μs, no practical maximum
  • Communication TCP / IP protocol
  • Trigger 3.3 / 5 V TTL pulse

Merlin Paper Merlin: a fast versatile readout system for Medipix3

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