VACUUM


Main objectives of the group are


  • Maintain Good vacuum


  • To perform wall conditioning


  • Various Coatings to reduce impurity levels.


  • Do gasfeed during plasma operation



ADITYA PUMPING SYSTEMS:


ADITYA pumping system includes two turbo molecular pumps and two cryo pumps, associated rotary vacuum pumps, ionisation gauges, quadrupole mass analysers, gate valves, gas leak valves and related power supplies. The systems are maintained efficiently so that the system runs continuously with minimum interruption. With all the four pumps operating, the base pressure of the system is ~ 8.0 X 10-8 torr. Along with this Gas analysers are installed to monitor residual gases during main plasma operation as well as during Discharge cleanings.


Wall Conditioning Techniques:


Thre are three kinds of wall conditioning implied on Aditya machine

  1. Electron Cyclotron Resonance (ECR)
  2. Pulsed Discharge Cleaning (PDC)
  3. Glow Discharge Cleaning (GDC)


GAS FEED MODES:


During main Plasma operation fuel gas can be fed to ADITYA in four different modes


  1. Continuous mode
  2. Pulsed Mode
  3. Molecular beam injection  (MBI) mode
  4. Gas puffing at any duration of plasma discharge.

Experiments:


  • Studies on effect of pre-ionization on discharges
  • Optimization of discharge cleaning
  • Helium discharge cleaning
  • Lithiumization
  • Gas puffing
  • Molecular Beam Injection (MBI)

Observations:


  • Oxygen level is reduced due to lithium coating.
  • The core density is improved by gas puffing using molecular beam injection.
  • Helium discharge reduced hydrogen recycling.
  • MBI injection incresed plasma density.

TEST STAND:  An UHV test stand and a helium leak detector are assembled to test any system for required level of vacuum and leak rate.


Vacuum Protocol: As per the protocol for maintaining good health of ADITYA vacuum system, all the subsystems to be connected to the vessel must be leak tested and then tested for vacuum less than 5 X 10 -9 torr.