Annual report 2002
In 2002, two new facility milestones were met, and a record number of shots were fired, in between moving all the H-1 support laboratories and workshops. The Laboratory also hosted/supported two international conferences, namely, The 13th International Stellarator Workshop held in Canberra, February-March, and the 11th International Congress on Plasma Physics held in Sydney in from 15-19 July.
The electron cyclotron resonance heating (ECRH) system delivered more than 150kW at 28GHz into H-1 in April 2002, producing the highest plasma energy to-date. Confirmation of temperatures awaits further data. The ECRH power supply capability has been extended from 10ms to 40ms. Another newly commissioned system has delivered 200 kW of radiofrequency (RF) power into H-1, meeting its own milestone, and doubling the range of magnetic fields accessible to argon plasma. Power at 1/2 Tesla to heat hydrogen plasma was increased to >120kW. This complements the 7 MHz RF system used to create plasma and heat both ions and electrons.
Impurity studies show that for our cleanest plasma conditions, light impurities (carbon and oxygen) are dominant. These conditions are achieved with ECR heating, or RF heating near a low order resonance in rotational transform. A low temperature vacuum baking system (maximum of 90C) has been commissioned, and initial tests successfully demonstrated a marked acceleration of outgassing of H2O, a major impurity. Gas control has been improved by installation of a five-way flow control system and a second puff valve. Around 4600 plasma shots were performed in 2002 of which half were in high field (0.5 Tesla) hydrogen/helium plasma.
In order to diagnose higher temperature plasma, new remote diagnostics are being commissioned, such as correlation spectroscopy for fluctuation studies and a second multi-channel Doppler spectroscopy system (MOSS). New automated scanning software allows data to be taken more efficiently and reliably, and a new Rogowski loop and 20-coil external magnetic probe (Mirnov) array provides measurements of plasma current and fluctuations. To simplify H-1 operation, installation of two additional PLC control systems has commenced.