Presentation on theme: "Cosmic Ray Research in India A Historical Perspective Suresh C. Tonwar Tata Institute of Fundamental Research, Mumbai Joined as Research Associate (August."— Presentation transcript:
Cosmic Ray Research in India A Historical Perspective Suresh C. Tonwar Tata Institute of Fundamental Research, Mumbai Joined as Research Associate (August 1962); Retired as Senior Professor (May 2006) Visiting Senior Scientist, Department of Physics, University of Maryland, College Park, MD 20742, USA Review Meeting GRAPES EXPERIMENT Cosmic Ray Laboratory (TIFR), Ooty; January 4, 2008
Cosmic ray particle physics (1940-80) Cosmic ray astrophysics (1980-.. )
Ground-based observations in 1920’s and 30’s by D.M. Bose, Vibha Choudhury et al in Kolkata. Balloon-borne observations by Homi Bhabha at I.I.Sc., Bangalore in early 1940’s. Tata Institute of Fundamental Research set up in June 1945 by the Dorabji Tata Trust and the Government of Bombay for research in nuclear sciences, including cosmic rays, and mathematics.
Cosmic Ray Research Centres in India Bombay (TIFR and BARC) Ahmedabad (PRL) Bangalore (IISc, IIA, RRI) Universities – Aligarh, Delhi, Durgapur, Gauhati, Jadavpur, North Bengal, Panjab, ….
COSMIC RAY STUDIES AT TIFR - Inspired and motivated by Homi Bhabha, observations on cosmic rays was a major research program in TIFR from its very beginning. A cloud chamber and trays of Geiger-Muller counters were in operation at TIFR as early as 1948 to observe muons traversing different materials (B.V. Sreekantan).
PRIMARY COSMIC RAYS : Studies on primary cosmic rays and particle interactions with nuclear emulsion stacks and particle detectors flown on balloon-borne platforms, launched from the National Balloon Facility, Hyderabad, during 1950’s and 60’s.
SECONDARY COSMIC RAYS: Measurements on the flux and angular distribution of muons at various depths underground in KGF during the early 1950’s using a 900 cm 2 area GM counter hodoscope (S. Naranan and B.V. Sreekantan). Observations on muon interactions in KGF using a cloud chamber (S.Naranan and B.V. Sreekantan). Direct studies on interactions of hadrons with carbon and brass targets during 1960-63 at Ooty using multiplate cloud chamber (A. Subramanian, S.Lal, et al.) Studies on hadrons in extensive air showers (EAS) during 1963-73 at Ooty (B.K. Chatterjee, S.C. Tonwar, R.H. Vatcha et al). Studies on high energy muons in EAS during 1963-83 at KGF (R. Srikanta Rao, B.S. Acharya, M.V. S. Rao, K. Sivaprasad et al). Studies on muons and neutrinos (and proton decay) during 1960-90 at KGF (M.G.K. Menon, S. Miyake, A.W. Wolfendale, P.V. Ramanamurthy, V.S. Narasimham, B.V. Sreekantan et al).
INTERACTIONS OF MUONS - In 1954, A.B. Sahiar, an expert on cloud chambers who received his training in Blackett’s laboratory in U.K., started a program for the study of muon interactions in an abandoned railway tunnel near Khandala in Western Ghats using a self-contained mobile cloud chamber laboratory which showed complete consistency of the observations with the expectations from quantum electrodynamics. These observations motivated Homi Bhabha to initiate a search for a new site for a high- altitude laboratory for studies on interactions of mesons and nucleons using cloud chambers.
COSMIC RAY LABORATORY AT OOTY - After careful evaluation of various possible sites spread all over the country, including Ooty and Kodaikanal in the south and Gulmarg in the north, the Cosmic Ray Laboratory of TIFR was set up at Ooty in December 1954, thanks to the generous offer by the then Governor of Madras, to Prof. Bhabha to use some of the building within the premises of the Raj Bhavan for the first experiments. The first observations on the interactions of muons and hadrons were made in late 1950’s here at Ooty using two multiplate cloud chambers placed one above the other. Ooty (11 o 23’ N, 158 o 55’ E, 2200 m) is also known as Ootacamund or Udhagamandalam (S. Lal, Yash Pal and A.B.Sahiar).
Direct studies on interactions of hadrons with carbon and brass targets during 1960- 63 at Ooty using a small multiplate cloud chamber (A. Subramanian, S.Lal, et al). Studies on hadrons in extensive air showers (EAS) during 1963-83 at Ooty using the scintillator-iron plates sandwich hadron calorimeter and the large multiplate cloud chamber (B.K. Chatterjee, S.C. Tonwar, R.H. Vatcha, B.V. Sreekantan et al).
Particle physics with cosmic rays – Results from observations on hadrons in air showers at Ooty Measurements were made on the arrival delay spectrum for hadrons, relative to the shower front, by timing the signals from the calorimeter. Detailed comparison of observations on delayed hadrons with Monte Carlo simulations led to the conclusion that the baryon production cross- section was increasing with energy (S.C. Tonwar et al).
Air Cherenkov Counter for particle identification (pion, proton, neutron) Multiplate cloud chamber with carbon and brass plates for interaction display 25-layer iron plate-scintillator calorimeter Direct Studies on Particle Interactions at Ooty (1960-63)
Arrival delay spectrum for hadrons in EAS – Increase in baryon production cross-section at 10 14-15 eV
Particle physics with cosmic rays – Results from observations on hadrons in air showers at Ooty Observations on high energy hadrons with the large multiplate cloud chamber provided unique and significant results on two aspects of high energy particle interactions. Energy spectrum of hadrons was found to be very steep, over the 100-1000 GeV range, requiring a significant increase in proton-air and pion-air interaction cross-section with increasing energy. Presence of a large number of neutral particles (mostly neutrons) among the high energy hadrons required an increase in the baryon production cross-section with increasing energy, a result obtained independently by the Ooty group from studies on arrival time distribution of lower energy, 10-20 GeV, hadrons (R.H. Vatcha et al).
Ooty cloud chamber: Single high energy hadron interacting inside the chamber
Ooty cloud chamber: Single high energy hadron interacting in the shielding above the chamber or in air
Ooty cloud chamber: Large number of hadrons incident on the chamber – core of an EAS
HIGH ENERGY MUONS - Observations in KGF mines in early 1960’s to obtain the ‘depth-intensity’ curve up to the largest depths possible. At the lowest depth (2760 m), no count was recorded in 60 days setting an upper limit of 10 -11 muons cm -2 s -1 sr -1. These measurements provided information on the interactions of very high energy muons, particularly the nuclear interactions and set a new lower limit on the mass of the intermediate vector boson mediating the weak interactions (M.G.K. Menon, S. Miyake, V.S. Narasimham and P.V. Ramanamurthy).
INTERACTION OF ATMOSPHERIC NEUTRINOS - The first direct observation of an interaction of an atmospheric neutrino within a detector was made in KGF in April 1964 by the DOT collaboration. This was followed by a similar observation a week later by the UCI-led collaboration (Fred Reines et al) in a mine in South Africa.
SEARCH FOR PROTON DECAY - The capability of the experiments carried out deep underground (> 2.3 km) in KGF mines for efficiently filtering all cosmic ray particles except neutrinos led the OCU-TIFR collaboration to install a 140-ton detector in 1980 to search for the decay of protons with a lifetime ~ 10 30 years as predicted by the Grand Unification Theory of Salam and Glashow. Unfortunately, the plans of the collaboration to upgrade this detector to enhance its sensitivity beyond 10 31 years were aborted by the decision of the GOI to close the KGF mines in early 1990’s due to economic reasons.
Cosmic Ray Research – High Energy Astrophysics Era (1977 – Present)
The ‘KNEE’ and the ‘ANKLE’ in the cosmic ray energy spectrum
Cosmic Ray Sources: Acceleration & Propagation Study of the elemental and isotopic composition of cosmic rays at GeV-TeV energies using balloon or satellite-borne detectors (E < 10 15 eV). Gamma ray astronomy over the GeV-TeV-PeV- EeV energies. Energy spectrum and composition around the knee (E ~ 3 x 10 15 eV). Energy spectrum and composition around the ankle (E ~ 3 x 10 18 eV). Energy spectrum and composition at energies ~ 10 20 eV and the observation of the Greisen- Zatsepin-Kuzmin cut-off in the energy spectrum.
Very High Energy Gamma Ray Astronomy at Ooty Atmospheric Cherenkov Observations (1967-83) A new phase of the search for TeV energy cosmic gamma ray sources started with the discovery of pulsars in 1967. First observations on the Crab pulsar at Ooty during 1968- 69 using a 2-reflector (0.9 m dia) system. The -telescope system was expanded to a 12-telescope array in 1977 and further to a 20-telescope array in 1979, in order to reduce the energy threshold for detection of cosmic gamma rays of energies less than 1 TeV.
20-Reflector (12 x 0.9 m dia + 8 x 1.5 m dia) Air Cherenkov Array at Ooty (1979)
IMPROVEMENTS IN THE ANGULAR RESOLUTION OF THE 20-TELESCOPE ARRAY (1981-83) The 20-reflector array was deployed in the ‘distributed mode’ to measure the arrival angle of each event to an accuracy better than 0.4 degree, to improve the signal to background ratio, during 1981-83 (Crab and Vela pulsars).
Central array of the 20-reflector air Cherenkov telescope array in the ‘Distributed Mode’ at Ooty (1981-83)
Outer array of the 20-reflector air Cherenkov telescope array in the ‘Distributed Mode’ at Ooty (1981-83)
Air Cherenkov Telescope Array at Pachmari (1990)
Air Cherenkov Telescope – 1 st of 6 Hanle, Ladakh (2005), 4250 m Altitude
Artist view of the planned air Cherenkov telescope array at Hanle (2007)
ULTRA-HIGH ENERGY GAMMA RAY ASTRONOMY AT OOTY (1983 - Present) UHEGRA became an active and exciting topic of research after the announcement of the discovery of a 4.8 hour modulated signal of UHE gamma rays from the X-ray binary source, Cygnus X-3, by the Univ. of Kiel group in early 1983.
GRAPES – 1 Experiment at Ooty (1984-87) (Gamma Ray Astronomy at PeV EnergieS) During 1983-84, the Ooty-EAS group improved the angular resolution of the Ooty-EAS array by installing new fast detectors and signal processing electronics with nanosecond response to improve its angular resolution. Observations during 1984-87 yielded positive results for Cyg X-3, Her X-1 and Sco X-1, but with low statistical significance.
GRAPES – 1 Experiment at Ooty (1984-87) The excess flux of showers observed by the Kiel group did not show the muon-poor signature as expected for gamma-ray initiated showers, leading to speculations about the nature of the radiation detected from the direction of Cygnus X-3. The GRAPES-1 array did not have any muon detectors and could not give additional information on the nature of the radiation detected from the direction of Cygnus X-3 and other sources.
GRAPES-2 Experiment at Ooty (1995 - Present) Ooty EAS array was expanded from 24 detectors to 100 detectors during 1987-89 and a 192-module muon detector (E > 1 GeV) was installed during 1989-92 to improve the sensitivity of the experiment for detecting gamma-ray initiated showers from cosmic sources. The GRAPES-2 array has been taking data continuously since 1992 to search for bursting sources of UHE gamma rays.
Muon multiplicity distribution expected for various primary nuclei (same E o ) – GRAPES-2 at Ooty
Muon multiplicity distribution expected for various primary nuclei (shower trigger) – GRAPES-2 (Ooty)
A comparison of the observed muon multiplicity distribution with simulations GRAPES-2 at Ooty
GRAPES-3 Experimet at Ooty (2000 – Present) – Phase 1 Primary Objectives: Observations on muon multiplicity distributions for small showers using the 16-module 560 m 2 area muon detector (E > 1 GeV) and the 217-detector air shower compact array. Determination of the energy spectrum of major nuclear groups (protons, He, CNO, Si and Fe) at low energies (30-300 TeV) overlapping with measurements by the balloon and satellite-borne detectors – validation of a proper high energy particle interaction model. Search for UHE gamma ray sources in steady as well as sporadic emission modes using the muon content as a discrimintor.
GRAPES-3 Experimet at Ooty (2000 – Present) – Phase 1 Secondary Objectives: Studies on solar cosmic rays and ground level enhancements to obtain the energy spectrum in the 20-100 GeV range. Search for exotic phenomenon such as air showers with time and arrival angle correlations between the GRAPES-2 and GRAPES-3 arrays.
GRAPES-3 Experiment at Ooty (Ongoing) – Phase 2 Determination of the energy spectrum of major nuclear groups (protons, He, CNO, Si and Fe) at energies around the KNEE (~ 3000 TeV) for obtaining information on the nature of the sources of UHE cosmic rays and the acceleration processes.
GRAPES-3 Experiment at Ooty (Near Future) – Phase 3 Expansion of the EAS array and the Muon detector for determination of the energy spectrum of major nuclear groups (protons, He, CNO, Si and Fe) at energies just below the ANKLE (~ 10 17 eV) for obtaining information on the physical processes causing the spectral change at the ANKLE.