[Sneap] Resistor strings needed

[Don Carter]

Toader, Ovidiu wrote:

>The ATF-SNEAP 2006 meeting was held in Australia and information is available at:
>http://www.ansto.gov.au/nugeo/conference/private/ATF_SNEAP.htm
>
>++++++++++++++++++++++++++++++++++++
>
>The SNEAP 2007 meeting will be hosted by Brigham Young University in Salt Lake City Utah. The meeting web site is located at:
>http://webpub.byu.net/wsd/.
>The 41st SNEAP Conference
>Brigham Young University
>October 7 - 11, 2007
>
>Please note:
>DUE TO THE ORIGINAL ANNOUNCEMENT BEING LOST IN CYBER-SP[ACE, THE
>SUBMISSION DATE HAS BEEN EXTENDED TO September 15th
> 
>Call for Papers: 
>
>Brigham Young University in sponsoring the 41st Conference of the
>Symposium of North Eastern Accelerator Personnel (SNEAP) on October 7-
>11, 2007. The conference will be held at the Embassy Suites Hotel in
>Salt Lake City, Utah.
>
>The SNEAP Conference is directed toward scientists and technical staff
>who are involved in developing, upgrading, and operating electrostatic
>accelerators. Further information about the conference is available at
>the conference website:
> 
>
>http://webpub.byu.net/wsd.
>
>
>We invite presentations on topics relating to accelerator design,
>operation, and improvement, and to unresolved problems with accelerator
>systems. Please send a title and abstract of your proposed presentations
>to sneap at byu.edu by September 15.
> 
>Contacts:
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>Lawrence Rees      sneap at byu.edu
>  
>
>
> ------------------------------------------------------------------------
>
> Greetings!
>
> We have serviced our General Ionex accelerator and we have many 
> resistors that are failing (mainly because of age)
>
> Does anyone have any resistor strings that were pulled out from a HVEE 
> machine and could give/sell some to us?
>
> We mainly need 140 MOhm strings (23 resistors each 6.2) and 506 MOhm 
> (23 resistors each 22 MOhm). O’Brien Scientific can give us some but 
> not enough (The resistors are rated 2 W).
>
> A source of such new resistors could also be valuable information for us.
>
> Thank you,
>
> Ovidiu
>
> MIBL, UM
>
> /*******************************************/
>
> /Ovidiu Toader,/
>
> /Manager, Michigan Ion Beam Laboratory/
>
> /University// of Michigan, Ann Arbor MI 48109/
>
> /http://www-ners.engin.umich.edu/research/Mibl/
>
> /ovidiu at umich.edu///
>
> /(734) 936-0166/
>
> /*******************************************/
>
> */Ex nihilo nihil ... (/**/Parmenides)/**//*
>
> /*******************************************/
>
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Ovidiu,

We have been modifying our 1200 megohm column resistors for our HVEC 4.5 MV
Tandem Accelerator at Ohio University by cutting away the tops of the 
epoxy resistor
assembly (spark gaps and all) and installing MaxiMox resistors from 
Ohmite Corp,
http://www.ohmite.com/cgi-bin/showpage.cgi?product=v_maximox . I think 
the first
test resistors were installed around April, 2006. We have been 
installing a group of
between 10 and 15 at each tank opening. We have 100 planes on our 
vertical column
and we have now replaced about 85% of the resistors with the modified 
ones. We have
run for weeks at voltages over 3.7 MV and have not noticed any 
electrical problems.
We did experience a few mechanical problems that we think were caused by 
vibrations
at specific points along the vertical column. The resistor leads would 
break from
mechanical fatigue. We seem to have cured this problem by epoxying the 
resistor
to the epoxy carcase at a single point along the resistor between the 
resistor and the old
resistor carcase.
We use the old resistor carcases that have failed as the mechanical 
assemblies to mount
the new resistors. We cut away the tops of the resistor assemblies 
removing spark gaps and
the top ends of the original resistors that were encapsulated in the 
resistor assembly. We leave
the top of a resistor near the middle of the assembly as a tie point for 
one end of two 500 megohm
resistors mounted in series. The other end of each resistor is attached 
to each end of the
resistor assembly. We chose these particular resistors because the 
series combination of the
two exceeds the required voltage and power requirements. We have not 
seen any electrical
problems with any of the resistors we have installed. They have not 
changed in value and do
not show signs of any high voltage stresses. Epoxying the resistor at a 
single point near the
middle of the new resistors seems to have caused the mechanical problem.
We are using the MOX-4-135006J I think (can't get to the resistor stock 
area at the moment).
These are 5 watt, 40 KV, 500 Megohm resistors.
I am attaching a picture of our first installed group of resistors 
installed in our vertical column.

don carter

Ohio University
Edwards Accelerator Lab
carter at ohio.edu
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