Front of crystals 75 mm back from front of flange according to Stepan's
diagrams.
On Wed, 14 Nov 2012, Maurik Holtrop wrote:
> Hi Sho,
>
> The beam enters at 30.52 mrad, if we believe the trajectories of the mapped fields as particles propagate through them in G4.
>
> When I made up the ecal geometry, the distance I was given was 51.93 inches from the target to the exit of the pair spectrometer vacuum chamber, so 1319mm. I just verified this and that is where I still have it in my simulation. That does not mean this is still the correct number though. I wouldn't worry about a mm though. I think it is more important that we verify the correct location of the front of the crystals. I am actually not 100% sure where they should be. We'll bring it up in the meeting tomorrow, and maybe Stepan or Takashi can chime in.
>
> Best,
> Maurik
>
>
>
>
>
>
> On Nov 14, 2012, at 8:34 PM, Sho Uemura <[log in to unmask]> wrote:
>
>> Okay, great, that clears up almost everything. A few last questions:
>>
>> * Beam enters at 30, 30.5, or 31 mrad? From Maurik's table it looks like 30.5, but I've heard all three of these numbers, so . . .
>>
>> * What is the distance between the target/lip of the magnet and the front face of the flange? Maurik's e-mail gives both 1319 and 1318 mm.
>>
>> * Where exactly is the electron flange in X?
>>
>> If there's an engineering drawing of the flange that would be nice, just so I can check it against the GDML of the flange.
>>
>> It looks like there was some discussion at the 10/18 software meeting
>> about things that needed to be done to the geometry, and among these were
>> ECal and ECal flange updates. Is there anything specific that was meant by that? Who was going to do that? Was anything actually done?
>>
>> On Wed, 14 Nov 2012, Stepan Stepanyan wrote:
>>
>>> Hello Sho,
>>>
>>> There were several email exchanges on the subject while I was trying to finish mine, so sorry for
>>> repeats. I attached a file with geometry of ECal, vacuum chamber and the analyzing magnet, slides 2 and 3.
>>>
>>> As for your numbers, (a) I remember 31 mrad, (b) if target is at the lip of the analyzing magnet and
>>> we take it as Z=0, than center of the analyzing magnet should be 18 inches away, 45.72 cm, (c) ECal
>>> is not symmetric around the magnet and Z-axis, (d) see ECal flange and hole locations in the attached
>>> file.
>>>
>>> I am also attaching another file showing positions at May run, that file has distance of crystals from the flange.
>>>
>>> I am sure you have seen these before, but just in case, it will help to finalize the geometry.
>>>
>>> Regards, Stepan
>>>
>>> On 11/13/12 9:35 PM, Sho Uemura wrote:
>>>> Those are sections, not perspectives. They should be literally what you would see if you cut through the detector at the specified z.
>>>> The flange appears to be positioned so the photon hole is somewhat to one side and angled out - if you look closely at the sections you can see that the photon hole is further from the center at z=150 than it is at z=137.
>>>> I've attached two perspective views of the whole geometry.
>>>> Relevant people, please comment on whether these statements are correct, with (0, 0, 0) being the beam spot on target and the Z-axis being parallel to the magnet bore:
>>>> * This is the frame we want to use for SLIC/LCSim.
>>>> * Beam enters at an angle of 30 mrad from Z, pointing into the positron side.
>>>> * Center of the analyzing magnet is at z = 45.22 cm.
>>>> * SVT is rotated 30 mrad into the positron side.
>>>> * ECal is completely symmetric around the Z-axis (aside from the missing crystals). Front face is at z = 137 cm.
>>>> * ECal flange has photon hole shifted 16 mm to the positron side at the front face of the flange (z = 135 cm), and 30 mm to the positron side at the rear face (z = 179 cm).
>>>> * ECal flange has electron bulge at the size and shape seen on my sections.
>>>> That's what I see in this geometry. If any of these statements are false, we need to fix the geometry to match.
>>>> On Tue, 13 Nov 2012, Maurik Holtrop wrote:
>>>>> Hello Sho,
>>>>> I am a little confused about the pictures that you are drawing. The top one seems to have a vacuum "bulge" area that is too small. The "bulge" is supposed to fill up the gap of all the crystals that were removed. Is that some effect of the perspective?
>>>>> The other issue is that the photon hole should be right through the center of the ECAL.
>>>>> Best,
>>>>> Maurik
>>>>> Looking along the beam line, +x towards the left, +y towards the top.
>>>>> On Nov 13, 2012, at 7:11 PM, Sho Uemura <[log in to unmask]> wrote:
>>>>>> Okay, here's some sections of the flange at different values of Z; center of viewer is (0,0) I think - I have no idea what I'm doing but I managed to get SLIC to display the geometry.
>>>>>> Looking at the Z=150 view, it looks like the photon hole is ~15 mm (somewhat more than one crystal width) from the center, where you'd want it to be at (150 cm)*(30 mrad) = 45 mm?
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