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Variable Energy Cyclotron Centre, Kolkata

Large Area Modular BaF2 Detector Array (LAMBDA)

LAMBDA is the acronym of Large Area Modular BaF2 Detector Array, developed to study the high energy gamma rays, coming from hot composite systems produced during heavy ion collisions. These photons are emitted at very early stages in the evolution or decay process of the hot compound system and can be efficiently used as a tool to study the diverse properties of hot and fast rotating nuclei. 

  

Barium fluoride (BaF2) crystal is a very fast scintillator with a high gamma detection efficiency. Therefore, it is the ideal choice for a high energy photon spectrometer where time-of-flight technique is to be employed for efficient neutron rejection.

Array Features:

* 162 individual detector elements.

* Large gamma detection efficiency.  

* Fast timing response (960 ps). 

* High Modularity to allow different geometrical configurations depending upon the experimental requirements. 

* Dynamic event reconstruction to reject cosmic muons and pile-up events. 

  

Each crystal has the dimension of 3.5 cm x 3.5 cm cross-sectional area and 35 cm long. The entire spectrometer was fabricated in house from the procured bare crystals. 

Electronics & Data Acquisition  

A dedicated electronics setup has been developed to register the energy and time information from each detector element in event by event mode. The latest commercially available high-density programmable CAMAC modules were used for its front end dedicated electronics. All electronics & DAQ were kept inside the experimental hall next to the array and were controlled from outside over Ethernet. 

  

The DAQ associated with the array is based on VME platform in a LINUX environment. High density (32 channels), fast VME QDCs and TDCs have been employed for energy and time measurements. It is capable of handling typically ~4000 events per second without appreciable dead time loss.