[Pafgbt] amplifier failures

[Bill Shillue]

Mark

we should know end of this week

You can talk directly to Steve White or Bob Simon

We agreed that we needed the 7-element central cluster at minimum, which they have been working hard at.  Everything else is in place.  Anish can speak about software but from his last update I think it is ready.

Bill    

________________________________________
From: Mark Whitehead [mwhitehe at nrao.edu]
Sent: Wednesday, July 24, 2013 10:21 AM
To: Bill Shillue
Cc: Brian Jeffs; Donald Bruce   Campbell (donald.campbell at cornell.edu); gcortes at astro.cornell.edu; pafgbt at nrao.edu
Subject: Re: [Pafgbt] amplifier failures

Hi Bill,

What is the plan for deciding whether or not to test FLAG on the GBT in
August?

Thanks,
Mark

> 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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