update on cryostation

Arash Hazeghi ahazeghi at stanford.edu
Fri Jun 6 15:38:07 PDT 2008


Thanks for reporting the issues.

 Regarding the back diffusion I will look at the pump and contact Varian,
this shouldn't be a problem if the pump is operating correctly since we
never had this issue before. There should not be back diffusion to the
extent that you can detect oil in the chamber, if this is the case the pump
has aged and gone bad, not that we need a dry pump.  

I checked the continuity between all probes at room T and they were OK, it
is very strange that you are not getting good contact my guess is you are
not touching the pads or as you mention there is a thin layer of something
on your sample and at low voltages this may be an issue since the tips are
really soft. Per your request, I will check this again. 

Now regarding the probe tips, All four probe tips were brand new and in
perfect shape when I replaced them just last week. I will look in the
logbook to see who used them. This is becoming a major issue, I cannot
replace the probe tips every week and our group will not pay for it.  Per
prof. Wong's suggestion from now on, whoever breaks the tips and don't
report it will not only have to buy new tips but will also be suspended from
the system for two weeks. No exceptions. 

Please be considerate when lowering and raising the tips. Never keep the
tips contacted to the sample or in close proximity before pumping down or
cooling. As the chamber goes to high vacuum the bellows  are stressed and
bow a little bit, as a result tips that are close to surface will crush or
may even run into each other. Position and lower the tips only when pressure
and temperature have been stabilized. Never lean on the table, yank the
cables or subject the system to mechanical shock when tips are in contact.
If users operate the probes according to the training these tips should last
for months.


Thank you all for your cooperation ,





Arash Hazeghi


PhD Candidate

Stanford Center for Integrated Systems

CIS-X 300, 420 Via Palou Mall, 

Stanford, CA 94305


phone: +1-650-725-0418

web: http://www.stanford.edu/~ahazeghi






From: yoshima73 at gmail.com [mailto:yoshima73 at gmail.com] On Behalf Of Yasuhiro
Sent: Friday, June 06, 2008 3:13 PM
To: Arash Hazeghi; Duygu Kuzum; shanbin at stanford.edu
Subject: update on cryostation


Hi all,

  Now the cyostation working at 77K very well. As Shanbin pointed out, it
seems that we had a contact issue between needle and metal pad due to very
hard condensed liquid (maybe vacuum oil back diffused into chamber). I just
replaced old vacuum oil of rotary pump. It turn into yellowish color
gradually. It seems to be important to replace it like once in 3 months.
Thanks for good suggestion, Arash! Another information are bellow. 


- new oil and container for old oil are near the cryostation. (Arash, could
you move to good position?)

- I still see some liquid (solid. maybe oil) on my samples. They look hazy.

- if you'd like to solve this problem permanently, I would recommend to
replace oil pump with diaphragm pump (this is dry).

- probe tips 3 & 4 are not working (it seems completely isolated). Arash,
please take a look at it! 

- probe tips 1 & 2 are bent and not comfortable.(It is not me...)




Yasuhiro Oshima
408-398-4753 (cell) 

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