W&M  report 05-25-2004

1) First drawings of the alignment of shielding wall, VDCs, scintillator and cerenkov detector

Based on Yongguangs GEANT results for the electron projection cuts for different Z positions
I have drawn in Solidworks the shielding wall with the openings and attached the detectors to the wall.

Here are Yongguangs X,Y electron profile cuts:

Z position [cm]	Xmin [cm]	Xmax [cm]	Ymin [cm]	Ymax [cm]	misc	X Projection [ps]	Y Projection [ps]
330	218	250	-72	+72	earliest(?) start of shielding wall	plot	plot
400	248	274	-82	+82	My end of wall according to drawings	plot	plot
430	260	284	-86	+86	official max end of wall	plot	plot
452.5	270	292	-90	+90		plot	plot
500	290	308	-96	+96		plot	plot
520	298	314	-100	+100	location of trigger scintillator	plot	plot

According to Yongguangs advice I extended the openings for 1cm in each direction. In addition I have drawn an envelope of the electron
projection, so I can see how the profile will behave downstream after the shielding wall.

Here is a 3D view of the alignment (click on pic). I have applied a vertical cut plane, so only the half lengths are shown:



On the left you can see the shielding wall with its openings. The green "wedge" is the envelope given by the opening, it's
the envelope of the elastic beam profile hitting the cerenkov from the table above plus a 1cm clearance border added.
The angle of  the mean electron track (dotted line) is 20.8 deg. The top and bottom aluminium frames/plates per VDC
are shown in red and define the maximun space needed so far. They are larger than the HV,gas and
wire planes because we have to allocate space for the preamplifier and flexible kapton readout foils.
 
Here is a side view with some dimensions (click on pics):





According to the drawing you will notice several items:

- the scintillator is fixed at z=520 cm, the cerenkov is fixed at z=530cm like proposed
- I have to tilt the VDCs by 45 degrees relative to the mean electron track with the freedom to tilt
by +45 or -45 degrees. As you can see, space is getting tight, so I have to save space by tilting like
it is shown in the drawing.
- Since we need ~30cm VDC  seperation for a ~0.6mrad angular resolution and the scintillator/cerenkov
is fixed in space/z-position, I can't place the VDCs with the shielding ending at z=430 cm. In this drawing
the shielding starts at Z=330cm and ends at Z=400cm, therefore the shielding is limited to a thickness of 70cm.
- the part David, Mike and I were surprised:
I had to open up the inner opening of the drift chamber from proposed 25cm up to 50cm in order to
avoid direct hits permitted by the shielding wall openings.
I have not checked how much the aluminium plate(s) will  reach into the next octant opening (overlap)

Mike Finn, David Armstrong  and I have to think about the VDC geometry  and your comments are welcomed:
    - Do we want to expose the VDC frame (G10/aluminium) to (in)elastic hits coming through
       the shielding wall openings ?

    To clarify this question it would help a lot to understand the simulation:
    => Which physical processes are included in this GEANT simulation?
                   - internal+external bremsstrahlung ?
                   - Multiple scattering (can it be turned OFF or ON?)
    => Shielding  openings:
                   - how much do they cut away from the inelastic tail

   Seems to me that we need :
     => electron profile in various z-positions (with Multiple scattering OFF/ON)
                    - defined only by the primary collimator
                    - defined  by hitting the cerenkov detector
                                     However, in the long term we have to insert the VDC into the GEANT code and see how
it it exposed to (in)elastic events and how this will affect the dilution measurement.
 
2) Ansys frame deformation simulation

Since the VDC inner frame size has doubled from 25cm to 50cm I checked with Solidworks/Ansys for the frame deformation.
Given an active area of 2100x500mm we will have 350 signal wire (6mm frame spacing). With an intended wire tension of 40g
the load on one frame side for a 25um Luma gold plated tungsten wire will be :

Load on one frame side: 40g*2100mm/6mm*10m/s2 = ~140N

Type of plastics	Young's or Tensile Modulus	comments
GE Plastics Noryl PPO 30% glass reinforced	7.76 GPa	stress cracks: http://ganesh.physics.lsa.umich.edu/~atlas/minutes/minutes000214.html
Quadrant Ertalyte unfilled	3.17 GPa
Quadrant Ertalyte TX lubricated	3.45 GPa
G10/FR4	22.4 GPa	depends on manufacture, large variations
Stesalam EP107-G118-40	30 GPa	HADES version of  "4411W"
Stesalam EP107-M950-40	(not listed in data sheet)	Stesalit's official definition of "4411W"

Left:   G10 deformation with 25cm opening, 15cm frame border and 140N load on one side, left and right side of frame is constrained in space
Right: same with 50cm opening and load on both sides (forgotten for 25cm setup)
      


And just for fun: the frame deformation for the VT HDC using Ertalyte (frame thickness 9.5mm)
Max frame deformation is ~26um, very close to the 24um calculated by Norm. BTW.: there is a out of plane deformation as well 




 Summary for a frame deformation (one side) with a force of 140N.

Material	Frame Border size [cm]	Frame inner width [cm]	Max Deformation [um] (one side)
G10	10	25	150
4411W	10	25
Noryl 30%	10	25	374
Ertalyte TX	10	25	1062
Structural Steel	10	25	17

Material	Frame Border size [cm]	Frame inner width [cm]	Max Deformation [um] (one side)
G10	15	25	40
4411W	15	25
Noryl 30%	15	25	99
Ertalyte TX	15	25	280
Structural Steel	15	25	5

Material	Frame Border size [cm]	Frame inner width [cm]	Max Deformation [um] (one side)
G10	15	50	47.5
Ertalyte TX	15	50	334
G10	20	50	22
Ertalyte TX	20	50	155
G10	25	50	12.2
Ertalyte TX	25	50	86

Conclusion: Seems we will stick to G10/FR4 since it is stiffer than Ertalyte.

3) Maximal wire defection due to gravity

Calculation a la Norm:

Tension [g]	Deflection [um], 25cm opening	Deflection [um], 50cm opening
30	8.7	17.5
40	6.5	13.1
50	5.3	10.5
75	3.5	7
100	2.6	5.25

4) Clean Room

Awaiting a quote from CRI (www.cleanroomsint.com) for a softwall clean room. The setup of the detector lab in the 2nd floor
is shown below. We have to take off  the current ceiling tiles and support structure in order to get enough clearance for the clean room fan units.
 
 

5) Misc

- Norm was so kind to send me his Solidworks drawings of the region 2 HDC chambers (thanks again!)
- I have emailed Stanislaw Sobczynski if we can get  his drawings of the magnet but I  have not got a response from him ...
- G0 checked their geometry defined in GEANT with an "euc2acad"  translator , which  seems to generate an AutoCAD 12
   script file from the euclid definition file.  I couldn't  get the translator  (Fortran code) compiled within ~2h and gave up for now
    ... reminds me of Garfield ...
   (The source of  the translator can be found here)
   
     => Do we have a CAD file (not a picture) from the collimator setup ?!
           (Tony explained me that the (this?) CAD picture was generated by GEANT)