Top view of the main apparatus

Atomic hydrogen and deuterium are produced in two triple differentially pumped beam lines. The beams enter the main chamber (pressure in 10-10 torr range), where there is a sample holder and a quadrupole mass spectrometer to detect species coming off the sample. The top line can be converted into a He beam line, producing a He supersonic beam (about 1-2% velocity resolution)Atomic hydrogen and deuterium are produced in two triple differentially pumped beam lines. The beams enter the main chamber (pressure in 10^-10 torr range), where there is a sample holder and a quadrupole mass spectrometer to detect species coming off the sample. The top line can be converted into a He beam line, producing a He supersonic beam (about 1-2% velocity resolution)

Side View of the main apparatus

Deuterium Beams

The beams are chopped by a mechanical selector to yield short pulses. At the top, D2 signal with radiofrequency turned off; at the bottom, undissociated deuterium (RF ON).

Hydrogen beam source

The source consists of a Pyrex tube, water-cooled, placed in a radiofrequency cavity consisting of a coil and a cylindrical shield. RF is fed into the cavity and hydrogen gets dissociated with efficiency of 75 to 90 %.The beam then goes through a collimator - which can be cooled to 150 K - and then into the first vacuum chamber of the beam line. Intensities of 1017 atoms/unit solid angle/sec are typically obtained.

Low Temperature Sample Holder

The low temperature sample holder consist of a block of OFHC (oxygen free high conductivity) copper. There is a small cavity behind the plate holding the sample: a constantan filament, supported by a ceramic bowl, works as a heater for the sample. Two thermocouples and a silicon diode are used to monitor the temperature of the sample. Measurements are typically carried out in the temperature range of 5-30 K. There is also a sample manipulator (not shown) for studies in the 150-1000 K sample temperature range.

List of Facilities

1. Atomic/Molecular Beam Scattering Apparatus
   1. Helium beam line, triply differentially pumped, with Helitrans cold finger for beam cooling. Velocity resolution of 1 percent. This line is now converted into a hydrogen beam line.
   2. Atomic hydrogen/deuterium line, triply differentially pumped (each); H/D source: RF discharge, water cooled, with 50 Watt 13 MHz power supply (each). Liquid nitrogen cooling for H beam.
   3. UHV scattering chamber with sample preparation chamber, pumped by 10'' cryopump, turbomolecular pump, titanium sublimation pump and ion pump. Low temperature sample manipulator that can be rotated and moved vertically, Helitrans cold finger; long travel VG sample manipulator (x-y-z motion, 2 rotations) - not used for these studies
   4. Detector: quadrupole mass spectrometer, differentially pumped, with cross beam electron ionizer mounted on a doubly differentially pumped rotatable detector flange. We have also a new high performance 3/4'' rod quadrupole mass spectrometer which is placed in the triply differentially pumped time-of-flight section off the main chamber.
   5. Other probes that can be placed in the main chamber: sputter ion gun, LEED/Auger optics and electronics; Molecular Beam Epitaxy liquid nitrogen shielded evaporation sources.
2. Data Acquisition
   1. EG-G Lock-in analyzers, model 5204 with CrystalHet and model 2806
   2. Time-of-flight electronics; multichannel scaler and LeCroy SA Fast Waveform Analyser
   3. Data acquisition: National Instruments Labview and EG&GMultiscaler
3. Sample Preparation
   1. Vacuum chamber for sample preparation (film deposition, sputtering)
   2. Bell-jar vacuum deposition system
   3. Transmission electron microscope available at SUNY-Upstate Medical Center
   4. X rays diffractometers (available on campus)
   5. Zeiss Optical Microscope ("Standard 16 Model")
   6. Crystal polishing facilities available in the College of Engineering
4. Computing Facilities
   1. Sun Sparcstation 5 workstation.
   2. DEC Alpha server in the Physics Department.
   3. IBM Pentiums and 486 computers.