THE NEW LLNL AMS SAMPLE CHANGER

The Center for Accelerator Mass Spectrometry at LLNL has installed a n ew 64 position AMS sample changer on our spectrometer. This new sample changer has the capability of being controlled manually by an operato r or automatically by the AMS data acquisition computer. Automatic con trol of the sample changer by the data acquisition system is a necessa ry step towards unattended AMS operation in our laboratory. The sample changer uses a fiber optic shaft encoder for rough rotational indexin g of the sample wheel and a series of sequenced pneumatic cylinders fo r final mechanical indexing of the wheel and insertion and retraction of samples. Transit time from sample to sample varies from 4 to 19 s, depending on distance moved. Final sample location can be set to withi n 50 microns on the x and y axis and within 100 microns in the z axis. Changing sample wheels on the new sample changer is also easier and f aster than was possible on our previous sample changer and does not re quire the use of any tools.