A DC HEAVY ION BEAM SOURCE WITH HIGH AVAILABILITY

THE OBJECTIVE OF THIS PROJECT IS TO DEVELOP A RELIABLE, COMPACT, HIGH CURRENT DENSITY, DIRECT CURRENT SOURCE OF COLDMASSIVE IONS FOR HEAVY ION BEAM PROBE (HIBP) SYSTEMS. THESE BEAM SYSTEMS HAVE BEEN USED SUCCESSFULLY TO MEASURE PLASMA POTENTIAL IN MAGNETICALLY CONFINED HIGH TEMPERATURE PLASMA. CURRENTLY, THE UTILITY OF THE HIBP DIAGNOSTIC IS BEING EXTENDED TO MEASURE FLUCTUATIONS OF SPACE POTENTIAL AND MAGNETIC FIELDS. HOWEVER, THE ABILITY OF AN HIBP SYSTEMTO MEASURE THESE FLUCTUATING PARAMETERS ON A SCHEDULE CONSISTENT WITH THE MAGNETIC FUSION PROGRAM'S NEEDS IS AT RISK BECAUSE OF THE UNRELIABLE NATURE, LOW CURRENT DENSITY, AND POOR OPERATIONAL CHARACTERISTICS OF THE ZEOLITE THALLIUMION SOURCE PRESENTLY USED IN THIS DIAGNOSTIC. THIS PROJECT PLANS TO SOLVE THE OPERATIONAL PROBLEMS OF A ZEOLITE ION SOURCE BY REPLACING IT WITH A RELIABLE, STEADY-STATE, INDUCTIVELY DRIVEN RADIO FREQUENCY (RF) DISCHARGE IN A HEAVYMETAL VAPOR, FROM WHICH A HIGH CURRENT DENSITY OF IONS CAN BE EXTRACTED. THE CANDIDATE MATERIALS INCLUDE MERCURY (HG),LEAD (PB), AND BISMUTH (BI) IN ADDITION TO THALLIUM (TI). THESE ADDITIONAL ELEMENTS ARE CHOSEN BECAUSE OF THEIR CLOSE PROXIMITY TO TI IN THE PERIODIC TABLE OF THE NUCLIDES. SOMEMAJOR DESIGN ISSUES THAT ARISE FROM USING THESE MATERIALS INAN HIBP ION SOURCE INCLUDE THE GENERATION AND CONTROL OF THEVAPOR PRESSURE WITHIN THE PLASMA CHAMBER OF THE SOURCE AND THE CONDENSATION AND MIGRATION OF MATERIAL IN THE REGION OF THE ELECTRODE STRUCTURE OF THE ACCELERATOR. THE SYSTEM REQUIREMENTS OF THE REFERENCE BEAM SOURCE ARE AS FOLLOWS: 200 MUA OF MASSIVE IONS AT ENERGIES RANGING FROM 10 TO 15 KEV, CIRCULAR BEAM WITH A HALF ANGLE OF BEAM DIVERGENCE <0.05 DEGREES, AND AVERAGE CROSS SECTIONAL AREA OF 0.1 TO 1 MM(2) OVER THE BEAM PATH. PHASE I OF THIS PROJECT AIMS: (1) TO ADDRESS THE DESIGN ISSUES ASSOCIATED WITH USING HG, TI, PB, AND BI VAPOR IN AN RF DRIVEN ION SOURCE, (2) TO SELECT THE ELEMENT THAT OFFERS THE GREATEST COMPATIBILITY TOAN HIBP SYSTEM, AND (3) TO PERFORM A CONCEPTUAL DESIGN OF A COMPACT, INDUCTIVELY DRIVEN ION SOURCE FOR THE TEXAS EXPERIMENTAL TOKAMAK HIBP SYSTEM.