[Pafgbt] amplifier failures

[Bill Shillue]

Brian et al

We are doing a lot of on the fly planning and scheduling unfortunately.  We could release you from the August commitment in GB, esp if it could benefit UMass.

One reason this might make sense for us is that we have spent more time on the current test campaign than we expected and staff might need a break from PAF just to get their other commitments caught up.

Bill
________________________________________
From: Brian Jeffs [bjeffs at byu.edu]
Sent: Thursday, July 18, 2013 11:14 AM
To: Bill Shillue
Cc: Karl Warnick; pafgbt at nrao.edu; Donald Bruce Campbell (donald.campbell at cornell.edu); gcortes at astro.cornell.edu
Subject: Re: [Pafgbt] amplifier failures

Hi Bill,

Sorry to hear of the amplifier problems on the PAF.  Does this change the likelihood of a GBT PAF test in August?  We are still trying to work out how to schedule use of our back end after the Arecibo tests (we are in Arecibo now working on setting things up).

We had talked about sending the system directly from here to Green Bank, but we have also heard from Neal Erickson at UMASS who would like to use it there for some initial data collection on his millimeter wave PAF.  That UMASS collaboration is providing all our current funding for backend development, but I told them we were headed to Green Bank first in August through early September.  What do you think would be a realistic schedule for Green Bank experiments given the amplifier problems?

Brian



On Jul 16, 2013, at 1:53 PM, Bill Shillue wrote:

> NRAO FLAG PAF has had some difficulties with amplifier failures recently.  The NRAO cryo amp uses an NXP Bipolar p/n BFU-725F. The failures appear to be due to cryo-cycling stress related.  This has slowed our progress toward GBT testing.  We are looking into the cause of the failure, and repairing and replacing affected amplifiers to try to progress with the PAF testing.  We have seen roughly ten failures, about fiver per cooldown over two separate cooldowns.  Prior to that we do not have good records of failure rates but we think it was rare, so it may be an issue that shows up after many cycles.  I am posting to PAFGBT because Steve White mentioned that Cornell was using a similar amplifier.
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