[time-nuts] hm H Maser

Bob Camp kb8tq at n1k.org
Wed Jan 11 12:18:54 UTC 2017


Hi

A cryo pump will get you into reliability issues if run 24/7. It also is doubtful 
that you will be able to maintain the vacuum level over long periods.

Bob

> On Jan 11, 2017, at 12:09 AM, Bruce Griffiths <bruce.griffiths at xtra.co.nz> wrote:
> 
> One could always use a cryo pump.
> The following paper is a summary of the current state of the art for rubidium vapour frequency standards:http://www.euramet.org/Media/docs/Repository/A169/IND55/micalizio_02182015.pdf
> 
> Bruce 
> 
>    On Wednesday, 11 January 2017 5:15 PM, Ole Petter Ronningen <opronningen at gmail.com> wrote:
> 
> 
> Add to this ion-pumps (in the case of EFOS type masers 2 every ~2 years),
> plus substantial tooling (turbomolecular vacuum pump, anyone?) to service
> the thing - unless you want the manufacturer to do so..
> 
> Ole
> 
> On Tue, Jan 10, 2017 at 11:12 PM, Dr. David Kirkby (Kirkby Microwave Ltd) <
> drkirkby at kirkbymicrowave.co.uk> wrote:
> 
>> On 10 January 2017 at 15:35, Ole Petter Rønningen <opronningen at gmail..com>
>> wrote:
>> 
>>> ... having said that, I for one think I'm with Bob on this one. The thing
>>> about masers are that they are big. At least active masers. And they
>>> require a substantial volume be kept at ultra high vacuum - which is not
>>> trivial, especially not in a homeshop. The cavity needs to be kept at a
>>> temperature stable to 0.001 degree C. With 4-5 magnetic shields. Add to
>>> this costly pumps to keep the vacuum this low even if you succeed at
>>> reaching that vacuum.. There's easily 1-2KUSD running cost per year just
>> to
>>> keep the maser running.
>>> 
>> 
>> Looking at the Microsemi MHM 2010 Active Hydogen Maser data sheet, the
>> maser has a peak power of 150 W and an operating power of 75 W.  Based on a
>> power consumption of 75 W, that is 657 kW hr / year of energy. I pay around
>> £0.20 (GBP) per kW hr for electricity, so that's £131 (GBP) annually. I
>> believe electricity is cheaper in the USA than here in the UK, but
>> converting £131 (GBP) to USD, that's around $161/year in electricity.. So
>> running costs don't seem to be an issue.
>> 
>> But I must admit, the thought of spending a lot of time/money to build
>> something I could have bought for a lot less with higher performance is not
>> that attractive, although of course there would be a satisfaction from
>> building it yourself.
>> 
>> Dave
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