atchan@aix01.aix.rpi.edu (Anthony C.T. Chan) (02/06/91)
Dear reader, Does anyone have tips on building a UHV-compatible electronic circuits? I am currently modifying a Scanning Tunneling Microscope for operation in the UHV and need to put the STM preamplifier in the UHV in order to minimize the noise. I understand that heat dissipation and outgassing from components could be a major problem. -- Anthony Chan :: atchan@rpi.edu :: anthony_chan@rpitsmts.bitnet Surface Physics Group, Physics Department, RPI, Troy, NY
whit@milton.u.washington.edu (John Whitmore) (02/06/91)
In article <'-^&7$|@rpi.edu> atchan@aix01.aix.rpi.edu (Anthony C.T. Chan) writes: >Does anyone have tips on building a UHV-compatible electronic circuits? >I am currently modifying a Scanning Tunneling Microscope for operation in the >UHV and need to put the STM preamplifier in the UHV in order to minimize the >noise. >I understand that heat dissipation and outgassing from components could be >a major problem. UHV, for the uninitiated, is ultra-high vacuum (generally 10^-10 torr, sometimes lower). While I cannot say for certain, I suspect that many transistor and some IC packages will be suitable at high vacuum; remember, the metal-package transistors we use today are built with glass/metal seals that were originally engineered for vacuum tubes. If the transistor leads are magnetic (most are), the lead material is likely Invar (and the package will be welded steel, as likely as not). Glass capacitors and glazed (or wire) resistors would outgas for a while but probably stabilize. Ceramic circuit board material is available for hybrids, certainly some compositions will be vacuum compatible. Your main problem is likely to be characterizing the various packages available to you; there is really no substitute to calling up the manufacturer's reps and asking for detailed material/package information. A more expensive alternative would be to weld a stainless steel box over the circuit, and use UHV ceramic/metal feedthroughs to get the signals and power in, making a sealed pod for the electronics that fits inside your vacuum vessel. I wouldn't recommend baking it TOO hot, so you might have a long wait before the vacuum gets really hard. Hope this helps. John Whitmore
phoenix.UUCP (Muyu Guo,,,) (02/06/91)
In article <'-^&7$|@rpi.edu> atchan@aix01.aix.rpi.edu (Anthony C.T. Chan) writes: >Does anyone have tips on building a UHV-compatible electronic circuits? >I am currently modifying a Scanning Tunneling Microscope for operation in the >UHV and need to put the STM preamplifier in the UHV in order to minimize the >noise. >I understand that heat dissipation and outgassing from components could be >a major problem. We have a STM with preamp sitting OUTSIDE of the chamber, preamp itself being enclosed in a Aluminum box to minimize the noise. There is a feedthrough to connect the preamp to the electrodes of the scanner. I don't know how much the noise can be further reduced to some level if the preamp is inside UHV chamber. -- Muyu Guo Princeton University
jtchew@csa2.lbl.gov (JOSEPH T CHEW) (02/11/91)
In article <'-^&7$|@rpi.edu>, atchan@aix01.aix.rpi.edu (Anthony C.T. Chan) writes... >Does anyone have tips on building a UHV-compatible electronic circuits? Tried E-mail but it bounced... You might want to get in touch with some synchrotron-radiation people. In your general area, the Cornell High-Energy Synchrotron Source (CHESS) and the National Synchrotron Light Source (NSLS) at Brookhaven come to mind. I'll even venture that E-mail to jacobsen@bnl.gov (Chris Jacobsen) will get you set on the right track. Tell him I sent you so he'll know who to yell at. :) Offhand, I can't think of anybody who has actually stuck their circuits right in the UHV, but doubtless someone has...certainly you should be able to get help with the general topics of bakeout, feed-throughs, etc. Good luck, --Joe "Just another personal opinion from the People's Republic of Berkeley"