Hello Daniel
I have tried to make some estimates in the attached document; the values
for the capacity of thin films NEG are pessimistic for the rough film,
since a factor of 3 can probably still be gained. One of the problems
could be methane, since it is not pumped by the NEG. For the other gases
the best solution seems to be  the St707, as yousay you can bake et
300C. 
I can try to redo the calculations by assuming 300eV electrons and
taking this time the real desorption coefficient , instead of estimating
only the total amount og available contamination to be desorbed.
Cheers
Mauro


Taborelli Mauro
TS-MME-SC
CERN 
1211 Geneva 23
tel ++41 22 767 35 02
fax ++41 22 767 83 80
-----Original Message-----
From: Daniel Kramer 
Sent: Monday, 19 June, 2006 12:00 PM
To: Mauro Taborelli
Cc: Bernd Dehning
Subject: Re: Secondary electron BLM

Hi Mauro,

- It seems like we can bake the BLMS at 300C without problems
- our Secondary Emission Yield is 0.055electrons/primary proton at
1.3GeV so the Secondary electron flux should be somehow 20 time lower
than the primary one.
So one might expect the currents of few nA in standard operation (50% of
these secondary electrons are expected to be low energy ones - below
300eV??)

PS: for the dose calculatioons I used continuous beam for 20 years as
somehow an upper estimate...

Cheers
Daniel

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Mauro Taborelli wrote:
> > Hello
> > I discussed with Paolo Chiggiato and the best solutions seems to be
> > strategies which do not imply coating of the parts but adding a sheet
of
> > NEG coating (as we already discussed, close to the wall of the box) or
a
> > strip of St707 NEG; the main difference is in the activation
> > temperature. If we put a NEG coating, making it rough (yes it works
also
> > on stainless stell in contrast to what I said yesterday) the acivation
> > temperature is around 200C, whereas with the St707 is around 300C, 24h
> > heating. I will try to evaluate again the gas load following different
> > assumptions to see the amount of NEG needed for that.
> > I have so two  questions:
> > -can you heat at 300C?
> > - what is the current of electrons impinging on the collector? This
> > might contribute also to the dynamic outgassing, unless the yield is
so
> > low that it is negligible with respect to the primaryy particles.
> > Cheers
> > Mauro
> >
> > Taborelli Mauro
> > TS-MME-SC
> > CERN 
> > 1211 Geneva 23
> > tel ++41 22 767 35 02
> > fax ++41 22 767 83 80
> >