[Halld-tagger] A different magnet for the Pair Spectrometer

Alexander Somov somov at jlab.org
Wed Aug 11 10:49:07 EDT 2010 

Dear Hrachya,

Most these studies are described in the gluex note
(including resolution dependence as a function of
the VC length). You can find the latest version in

http://www.jlab.org/~somov/pair_spectrometer/ps_micro_note.pdf

The resolutions/rates/(impact from the beam spot size) can be
scaled to any predefined Bl using this note.


I have also studied background for the magnet with the
smaller aperture (larger momentum of accepted leptons),
10D37 magnet, using detailed Geant simulation; the
coincidence bg was found to be below 1% - details were
discussed during the last beamline meetings (I haven't
yet added results to the write up)

Regards,
         Sascha


P.S. 18D36 seems to be a good magnet candidate to use
(it's used in the Hall-B ps). Bl is large, there should
be no problems operating it at 1.5 Tm; it can be well suit
for both Si or GEM. Many details have been discussed
during the last beamline meeting...





On Wed, 11 Aug 2010, Hrachya.Hakobyan wrote:

> Dear Eugene,
>
> The previous design of PS was made within electronics saving
> limitations and  without use of magnetic field variation.
>
>  Some detector and readout simulations primary are needed to evaluate an
> impact of BL lowering to the energy resolution due to increase of
> multiple scattering and beam size influence, as well as the contribution
> of accidental coincidences.
>
>  Some compensation of analyzing power lost  may
> be compensated by increase of  vacuum chamber length.
>
>  As a electronics  saving approach the use of smaller area  SI,GEM
> detectors in combination with magnetic field scan may be alos
> accessible.
>
> Best Regards, Hrachya
>
>
>
> On Fri, 6 Aug 2010, Eugene Chudakov wrote:
>
>> We are considering a smaller magnet for the pair spectrometer:
>>  18D36 instead of 30D72. It weighs 20t instead of 65t. It can
>> be split in two parts. It is a much easier magnet to handle.
>>
>> The gap size is 18(X)x6(Y)x36(Z) inches. The field is
>> 2.0T at 2.2kA. We would shim the gap to 3", which would
>> provide 2.0T at about 1.2kA.
>>
>> The magnet would provide a field integral up to 1.8Tm. At 1.8Tm
>> the acceptance goes down to 4 GeV of the electron energy.
>> The plan is to use a coordinate detector (a GEM is considered),
>> at a lower field integral.
>>
>> The BNL has several magnets of this type and old power supplies
>> for them. The same magnet is being used by PRIMEX in Hall B.
>>
>> Let me know if you have concerns with this change.
>>
>> Eugene
>>
>> ------------------------------------------------------
>> Eugene Chudakov
>> http://www.jlab.org/~gen
>> phone (757) 269 6959  fax (757) 269 6331
>> Thomas Jefferson National Accelerator Facility
>> 12000 Jefferson Ave,
>> Newport News, VA 23606 USA
>>
>> ---------- Forwarded message ----------
>> Date: Thu, 5 Aug 2010 21:36:16 -0400 (EDT)
>> From: Eugene Chudakov <gen at jlab.org>
>> To: "Pendzick, Alexander F" <pendzick at bnl.gov>
>> Cc: Alexander Somov <somov at jlab.org>, Liping Gan <ganl at uncw.edu>,
>>     "Pile, Philip H" <pile at bnl.gov>, Timothy Whitlatch <whitey at jlab.org>
>> Subject: RE: Magnet 30D72
>>
>> Al,
>>
>> thanks for the information.
>>
>> we are seriously considering taking this magnet (18D36) instead of
>> the big one we initially planned (30D72). We need one magnet.
>> We are also considering borrowing a power supply. What is
>> the status of these magnets? Do we need to test it or you have some
>> which have been tested recently? Have you by chance a magnet with shimmed poles
>> (to about 3")?
>>
>> Thanks again,
>> Eugene
>>
>> On Thu, 5 Aug 2010, Pendzick, Alexander F wrote:
>>
>>> Eugene
>>>
>>> 	 An 18D36 Mk II weighs 20 tons and can be split in half. It will
>>> reach 2.2T at 3000a, with a 6" gap --2T at ~2230a. It is approximately
>>> linear up to 1900a.
>>> 	We have field maps, etc.
>>> 	We have power supplies available but they are old.
>>>
>>> 	Liping borrowed one of these magnets --she should have data
>>> also.
>>>
>>>
>>> Al
>>>
>>>
>>> -----Original Message-----
>>> From: Eugene Chudakov [mailto:gen at jlab.org]
>>> Sent: Wednesday, August 04, 2010 3:40 PM
>>> To: Pendzick, Alexander F
>>> Cc: Alexander Somov
>>> Subject: RE: Magnet 30D72
>>>
>>> Al,
>>>
>>> thanks, it is a good news.
>>> Have you some documentation/information on this magnet?
>>> We found something but are not sure it describes the magnets
>>> you have.
>>>
>>> a) Is it in one 20 t piece? Can it be split in two for transportation
>>>    and poles' work (we would reduce the gap to about 3 inches)?
>>>
>>> b) What current is needed with the normal configuration to provide
>>>    2 T at the center?
>>>
>>> c) Is there a magnitization curve? What is the linear region?
>>>
>>> d) Is there a field map measured?
>>>
>>> d) Have you also an excess power supply to use with this magnet?
>>>
>>> Thanks again for your help,
>>>
>>> Eugene
>>>
>>>
>>> On Wed, 4 Aug 2010, Pendzick, Alexander F wrote:
>>>
>>>> Eugene
>>>>
>>>> 	We have many 18D36's and they are in good shape  ---
>>>>
>>>>
>>>> Al
>>>>
>>>>
>>>> -----Original Message-----
>>>> From: Eugene Chudakov [mailto:gen at jlab.org]
>>>> Sent: Wednesday, August 04, 2010 12:23 PM
>>>> To: Pendzick, Alexander F
>>>> Cc: Liping Gan; Pile, Philip H; Alexander Somov
>>>> Subject: RE: Magnet 30D72
>>>>
>>>> Al,
>>>>
>>>> thank you very much for your help.
>>>> We still hope to find a smaller magnet than one we originally
>>>> planned to use. We found another two candidates in the same list:
>>>>
>>>> 18D36 and 18D40
>>>>
>>>> Is any of these magnets available?
>>>>
>>>> Thank you,
>>>> Eugene
>>>>
>>>> ------------------------------------------------------
>>>> Eugene Chudakov
>>>> http://www.jlab.org/~gen
>>>> phone (757) 269 6959  fax (757) 269 6331
>>>> Thomas Jefferson National Accelerator Facility
>>>> 12000 Jefferson Ave,
>>>> Newport News, VA 23606 USA
>>>>
>>>> On Tue, 3 Aug 2010, Pendzick, Alexander F wrote:
>>>>
>>>>> Eugene
>>>>>
>>>>> 	We have not been able to find that magnet ----I believe we got
>>>>> rid of it a few years ago.
>>>>>
>>>>>
>>>>> Al
>>>>>
>>>>>
>>>>> -----Original Message-----
>>>>> From: Eugene Chudakov [mailto:gen at jlab.org]
>>>>> Sent: Friday, July 23, 2010 7:08 PM
>>>>> To: Pendzick, Alexander F
>>>>> Cc: Liping Gan; Pile, Philip H; Alexander Somov
>>>>> Subject: RE: Magnet 30D72
>>>>>
>>>>> Dear Al,
>>>>>
>>>>> do you have by chance another excess magnet: 20D47 ?
>>>>> We found its parameters on a WWW page and realized it would also
>>>>> fit our requirements and should be much easier to handle.
>>>>>
>>>>> Thanks,
>>>>> Eugene
>>>>>
>>>>> ------------------------------------------------------
>>>>> Eugene Chudakov
>>>>> http://www.jlab.org/~gen
>>>>> phone (757) 269 6959  fax (757) 269 6331
>>>>> Thomas Jefferson National Accelerator Facility
>>>>> 12000 Jefferson Ave,
>>>>> Newport News, VA 23606 USA
>>>>>
>>>>> On Thu, 10 Jun 2010, Pendzick, Alexander F wrote:
>>>>>
>>>>>> Eugene
>>>>>>
>>>>>> 	A few issues associated with your proposed tests:
>>>>>>
>>>>>> 	These magnets weigh more than our crane capacity, therefore they
>>>>>> are presently split and will have to be assembled.
>>>>>>
>>>>>> 	The only water we have available in the building they are in is
>>>>>> domestic water ---- ~ 15 GPM @50 psi
>>>>>>
>>>>>> 	To look for turn to turn shorts, we normally pulse the coils out
>>>>>> of the cores --- are you interested in doing this?
>>>>>>
>>>>>> 	Will you be bringing a DC power supply?
>>>>>>
>>>>>> 	While we generally recognize your training --- your test plan
>>>>>> may include exposed bus tests  -- this will be a problem.
>>>>>>
>>>>>> 	Late summer is best for us, I believe there is interest in one
>>>>>> of our spectrometer magnets--a 48D48 --- You may want to combine
>>>> these
>>>>>> visits.
>>>>>>
>>>>>>
>>>>>> Al
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> -----Original Message-----
>>>>>> From: Eugene Chudakov [mailto:gen at jlab.org]
>>>>>> Sent: Wednesday, June 09, 2010 5:20 PM
>>>>>> To: Pendzick, Alexander F
>>>>>> Cc: Pile, Philip H; Timothy Whitlatch; Liping Gan; Alexander Somov
>>>>>> Subject: Magnet 30D72
>>>>>>
>>>>>> Dear Alexander,
>>>>>>
>>>>>> there is an agreement to transfer a excess magnet 30D72 from the BNL
>>>>> to
>>>>>> the Jefferson Lab. I just talked to Phil Pile on this matter and
>>>>>> he suggested to coordinate the details with you.
>>>>>>
>>>>>> We are planning to test several things before shipping the magnet,
>>>>>> namely:
>>>>>>
>>>>>> (1) Insulation check,
>>>>>> (2) Water leakage,
>>>>>> (3) Hipot,
>>>>>> (4) Coil test at a low current.
>>>>>>
>>>>>> Please let me know what would be the best time to fit
>>>>>> this work into you schedule. Our preference is to get ready for
>>>>>> shipment by the end of this summer.
>>>>>>
>>>>>>> From our side this activity will be coordinated by
>>>>>> Liping Gan  <ganl at uncw.edu>.
>>>>>>
>>>>>> Thank you,
>>>>>>
>>>>>> Eugene
>>>>>>
>>>>>>
>>>>>>
>>>>>> ------------------------------------------------------
>>>>>> Eugene Chudakov
>>>>>> http://www.jlab.org/~gen
>>>>>> phone (757) 269 6959  fax (757) 269 6331
>>>>>> Thomas Jefferson National Accelerator Facility
>>>>>> 12000 Jefferson Ave,
>>>>>> Newport News, VA 23606 USA
>>>>>>
>>>>>
>>>>
>>>
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