SNEAP 1999 Lab Report



Reporting period October 1998 thru October l999  
Tom J. Gray and Robert D. Krause

James R. Macdonald Laboratory
Kansas State University
Manhattan, KS 66506-2604

Tandem Operations

This report covers the period of October 1998 through October 1999 for the James R. Macdonald Laboratory at Kansas State University. The EN tandem Van de Graaff accelerator has operated very well during this reporting period. Tandem maintenance has been routine with no serious tandem problems.

In October 1997 we ordered a charging belt replacement for the tandem but found that the vendor could not supply a belt. As we were approaching 6000 hours of operation on our present charging belt, and knowing that the lifetime of a charging belt under normal operation is approximately 10,000 to 12,000 hours, we initiated procedures to replace the present belt charging system with a NEC pelletron charging system. That system has been ordered and the current plans call for the changeover from belt charging to pelletron charging to take place in the summer of 2000.

During this reporting period the tandem has logged 3,061 hours of actual beam time operation. The amount of down time during this reporting period has totaled 152 hours, which accounts for three tandem openings.

Ion Sources

The EN tandem Van de Graaff accelerator can be injected by either of two different ion sources. The Middleton high intensity sputter source operates 90% of the time, and the diode ion source is used the remaining 10% of the time. The diode source was used to produce primarily beams of hydrogen and fluorine; the Middleton source was used to produce primarily beams of hydrogen, boron, carbon, oxygen, fluorine, silicon, copper, chlorine and iodine.


The LINAC has been in service throughout the year. We have had some problems with low resonator maximum achievable fields in two of the high beta resonators. Preliminary analysis of the resonator performance suggests that the resonators may have cracked ports, which would limit the maximum field levels to the order of 1 MV/m for those resonators. There is a known existing problem with the ATLAS Nb split-ring resonators wherein the welds on the rf and/or VCX ports on the resonator body can crack.

The LHe system has been operating continuously essentially problem-free. We do have oil leakage at the compressor shaft seal on the input drive shaft. We have tried several different seals without success in reducing the leak for any extended period of time. The compressor has been running for 12 years, and though there is the shaft seal leak problem, it continues to be reliable.

We have provided time-bunched heavy ion beams for experiments on the LINAC several times during the past year. One experiment scheduled for early near year will require that low energy B3+ ions be accelerated, increasing their energy from 3 MeV to 5 MeV. Because of the large velocity mismatch of the 3 MeV B ions, we will have to run the LINAC at its maximum operational level to provide the beam as requested.


This work was supported by the Division of Chemical Sciences, Office of Basic Energy Sciences, Office of Energy Research, U.S. Department of Energy.


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