[esa-t474] All corrections to T474 paper complete

[Yury Kolomensky]

	Hi Mark,

On Mar 29, 2008, at 1:08 PM, Mark Slater wrote:
> Thanks for the comments, Yury. I have ammended the reply to points  
> 2 and
> 11 and changed the specs. I would be very grateful if this was  
> checked to
> make sure I'm not talking rubbish!
>

Have you update the draft as well ?

> Chris A.: Has there been a direct measurement of the coupling for BPMs
> 3-5?
>
> Yury: What are the specs for the front-end filter (the one centred at
> 2856)?
>

These are two types of filters. For dipole cavities in BPMs 31-32,  
41-42 and 9-11, we used 4-pole cavity Filters, RLC Model  
CBPF-2856-20-4-R. 2856 MHz center frequency, 20 MHz bandwidth. For  
BPMs 3-5, and Q cavities in other BPMs, we used 3-pole RLC filters  
with 100 MHz bandwidth, model BPF-500-2856-100-3-RF


> Thanks,
>
> Mark
>
>
>
>
>>> ********************************
>>> 2) In several places (line 178 on p. 12, and later, in lines 671  
>>> to 674 on
>>> p. 42, line 587, p. 35), the paper talks
>>> about unwanted coupling with other modes
>>> in the cavity. BPM 1 is said to have rectangular cavities, and I am
>>> guessing that the mechanical damage brought the
>>> detuned orthogonal mode closer to the
>>> filter acceptance window.  Is the artifact in the BPM 4x signal  
>>> due to the
>>> same issue? In that case, analysis of the
>>> residual vs. motion in the y-direction
>>> would give a much clearer indication of the source of the cross- 
>>> coupling
>>> (if data is available).
>>>
>
> MWS: The damage to the cavity seems to have allowed the orthogonal  
> mode to
> be accepted by the coupler due to the change in geometry. In  
> general, the
> coupling in the rectangular cavities (1-2, 9-11) will be dominated  
> by the
> proximity to neighbouring cavities (around -30-40dB). There would be
> direct coupling for the cylindrical cavities but this was measured  
> to be
> at a similar level. At the offsets recorded (~200um), it is highly
> unlikely we would see a coupled signal in the orthogonal channel.  
> During
> calibrations (mover or corrector) when the offset was larger, any  
> residual
> seen is almost certainly going to be dominated by relative rotation  
> errors
> between the axes of the beam/BPM movement and the couplers making it
> difficult to measure from the beam data.
>

Not sure if this discussion of the coupling is sufficiently  
descriptive or will raise other issues, but sounds OK. As for the  
orthogonal mode, I am not entirely sure if this interference in BPM 1  
is due to the X-dipole mode coupling to Y or vice versa (the natural  
separation is over 100 MHz, which seems large to significantly  
shifted by the mechanical damage, but possible). We do observe two  
modes in BPM41-Y with a network analyzer, separated by about 3 MHz.

Yury