E-rhic-ir-l mailing list

["Berg, J Scott" <jsberg AT bnl.gov>]

Bother. If the spin were not totally destroyed if we ran with the snakes off, we could accelerate with the snakes off, ensure the beam is on the BPMs in exactly the same positions as it is with the snakes on (if possible?), and do the measurement like that. Even if the snakes generate some path length difference themselves, the RF frequency tells you what that is and isolates it to the snakes themselves if the beam is at the same position everywhere else.

 

-Scott

 

From: E-rhic-ir-l <e-rhic-ir-l-bounces AT lists.bnl.gov> On Behalf Of Ptitsyn, Vadim via E-rhic-ir-l
Sent: Monday, February 22, 2021 10:34 AM
To: Willeke, Ferdinand <willeke AT bnl.gov>; E-rhic-ir-l AT lists.bnl.gov; Aschenauer, Elke <elke AT bnl.gov>
Subject: Re: [E-rhic-ir-l] IR to do list

 

I agree with Ferdinand, that resonance depolarization might be used in our case to determine electron energy.  One can point out that the technique is so accurate that it allowed to see the effect of moon tides on the beam energy in LEP.   An RF dipole has to to be added into the ESR for this measurement. But in our case we would need to evaluate the effect of spin rotators on the measurement accuracy, since the rotators modify slightly the dependence of spin tune on the beam energy.

 

For protons the Siberian snakes eliminate the spin tune dependence on the beam energy (in fact, that is one of main purpose of the Snakes). Hence, the energy measurement using spin resonance approach can not be directly used.

 

 

With best regards,

                                      Vadim Ptitsyn

                                      Electron-Ion Collider Project

                                      Brookhaven National Laboratory

 

 

 

 

From: E-rhic-ir-l <e-rhic-ir-l-bounces AT lists.bnl.gov> on behalf of Willeke, Ferdinand via E-rhic-ir-l <e-rhic-ir-l AT lists.bnl.gov>
Date: Monday, February 22, 2021 at 10:04 AM
To: Aschenauer, Elke <elke AT bnl.gov>, E-rhic-ir-l AT lists.bnl.gov <E-rhic-ir-l AT lists.bnl.gov>
Subject: Re: [E-rhic-ir-l] IR to do list

Elke, the storage rings are huge spectrometer systems. We know the beam energy to the extent we know the absolute strength of the dipole magnets.

(this could be determined to 1E-4 for a single reference magnet together with 1E-4 relative precision referring to the reference magnet for all magnets.)

We also must include orbit data and corrector strength in the analysis.

What is the precision, the experiment needs?

You might remember that one can use spin depolarizing resonances for higher precision for the electron beam (done for the exact mass of the Y in Doris and SPEARS).

Ferdinand

 

From: E-rhic-ir-l <e-rhic-ir-l-bounces AT lists.bnl.gov> On Behalf Of Aschenauer Elke-Caroline via E-rhic-ir-l
Sent: Monday, February 22, 2021 9:40 AM
To: E-rhic-ir-l AT lists.bnl.gov
Subject: [E-rhic-ir-l] IR to do list

 

Good Morning,

 

I thought the discussion on Friday was very good and it would make sense to generate a "to do list” accessible for everybody 

and document how a specific item has been resolved.

 

I have been thinking a bit more about the points over the weekend and actually I have one more for the list we talked about the uncertainty on the overall beam energy, this will be very important for the  physics as we rely on knowing the beam energy.

 

The other item I think we need to make a decision is that we really do as discussed on friday the solenoid compensation scheme without introducing vertical kicks at the IP.

 

Thanks elke

 

 

 

 

 

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