After the successful operation of single crystal HPGe detector arrays at Nuclear Science Centre
(now known as Inter University Accelerator Centre), New Delhi and the Tata Institute of Fundamental Research,
Mumbai, there was a need to upgrade these arrays. It was felt that the next generation arrays within the country
should have composite detectors which would provide us an unique advantage of an increased the efficiency
as well as the polarization measurements.
As a part of it's IXth plan, IUC-DAEF, Calcutta Centre (now known as UGC-DAE,CSR Kolkata Centre), Tata Institute of Fundamental Research, and Saha Institute of Nuclear Physics procured about 6 Clover detectors & their Anti-Compton shields. Since these detectors were costly and the use of these detectors demanded pooling of available resources, there was an underlying need to form a National Collaboration to set up an array comprising of Composite detectors.
First attempts to set up a modest Clover array in collaboration with other Insituties and Universities were initiated by IUC-DAEF,CC, with TIFR & Andhra University. A 5 clover array was jointly setup at TIFR, Mumbai in 1999. Two of the clover detectors were successfully transported from Kolkata to Mumbai and back. This exercise cleared all doubts regarding the feasibility for the transportation of these delicate and extremely fragile detectors. Two experiments were performed and the success of these experiments paved way for the formation of a Nationalcollaboration between IUC-DAEF,CC, VECC, SINP, NSC, TIFR and the Universities to pool the available resources (man-power as well as the detectors) to setup a multi clover array, the Indian National Gamma Array (INGA).
An eight clover array viz Indian National Gamma Array-I (INGA-I) was setup in collaboration with the Universities & Institutes at the 14 UD Pelletron facility at TIFR Mumbai in April 2001. Two Clover detectors along with their Anti-Compton Shields were transported from Kolkata by IUC-DAEF,CC and SINP for these experiments while Nuclear Science Centre & SINP also pooled in considerable electronic modules. All collaborating groups actively participating in the installation and operation of the array during it's stay at TIFR Mumbai.
INGA-II The second phase of INGA was made operational at the 15 UD Pelletron Accelerator facility at NSC, New Delhi, in 2002. INGA then comprising of 8 clover detectors was coupled to the HIRA (recoil-mass seperator) . Of these 8 clovers two each were transported from TIFR, SINP & IUC-DAEF,CC. A charged particle ball and a few of neutron detectors were also coupled to the facility.
Two of the experiments were successfully performed wherein the power of the clover array was complimented by the sensitivity and selectivity of a charged particle ball in one experiment to investigate a relatively weak yet intriguing reaction channel and the recoil seperator in the another experiment to perform unique lifetime measurements of micro-second isomers.
INGA-III After the successful completion of the initial two phases of operation at TIFR and at NSC, the array was setup at VECC, Kolkata. The Early Implementation of the Array comprised of 6 clover detectors which were locally pooled. The beams of inert gases from the ECR coupled to the room temperature cyclotron were available for the first time in the country for experiments. Also the energy regime of the beams was unique which allowed us to populate nuclei at higher angular momentum using non-equilibriated reaction mechanisms.
Partial INGA Collaborations In between the various phases of INGA the various collaborating institutes would pool up the available resources and perform experiments preserving the spirit of national collaboration. At TIFR a 7 clover array was setup in collaboration with SINP, UGC-DAE CSR,KC , IUAC, VECC and IIT Roorkee.
INGA-IV The near complete INGA array was installed in the new beam hall at IUAC, New Delhi. In 2008. The array was made operational with about 18-20 Clover detectors. The individual shields subtend approximately 30 degree angle at the target. The total photopeak efficiency of INGA is ∼ 5%.
Several developmental activities have been undertaken as a part of INGA. These are