# Solid Baffle

(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)

This page has been moved to https://solid.jlab.org/wiki/index.php/Baffle in the new SoLID Wiki. Please do not edit this page.

## New Idea

New Idea: can we have the baffles straight where the detectors are and more curved near the target? Now the spokes are straight near the target. The detectors would then have a simpler geometry, reducing cost. Anyway, we need a Monte Carlo to check out new ideas. (by Paul Souder?)

## Zhiwen's work with geant4 simulation

### Verify Eugene baffle acceptance

Eugene's result is at PAC 34 Proposal page 36

#### condition

beam e-/gamma/e+, E 0-11GeV, Theta 22-35 degree, Phi 360 degree,

Vertex centered at 10cm, 40cm long full target or point target

baffle 6 plates, 30 slits per plate, 20 blocks per slit.

baffle plates are located at 30, 60,90,120,150,180 cm.

tracks killed once hit on baffle, observer plate at 210 cm.

FLUX bank was used to determine the average Z vertex, this is not meant to be a very accurate vertex, but good enough to tell the hits on which plate.

#### beam e- with full target

hits on baffle
XY of hits on each baffle plates
Z of hits on each baffle plates
hits on observer plate
Generated particle Mom
acceptance VS Mom at observer plate
hits on baffle (beam 1.5GeV)
hits on baffle (beam 0.38GeV)

#### beam e- with point target

acceptance VS Mom at observer plane

#### beam e+ with full target

hits on baffle
hits on observer plate
acceptance VS Mom at observer plate

#### beam gamma with full target

hits on baffle
hits on observer plate
acceptance VS Mom at observer plate

#### result and questions

• the results are different from what Eugene had
• Eugene's result is flat between 40-50%, we have point target result flat at 40-50%, full target at 30%-40%. But according to the proposal, I think Eugene simulate the full target.
• Eugene's electron result drops slower below 2GeV. But ours drop to 0 at 2GeV. for example, at beam 1.5GeV, all tracks are blocked as shown the hit plot.
• at beam 0.38GeV, we have some acceptance as shown in the hit plot. Eugene's plot doesn't show P<0.5GeV, so we don't know what he had.
• Eugene has pion result also. I guess it's negative pion, but it should have the result like electron because magnetic bending doesn't care mass, only charge. So did Eugene have detailed physics in simulation?
• neutron particle is not blocked well, 40% acceptance.
• positive particle has acceptance about 20-30%

#### note about Eugene's study

• The acceptance study has real physics turned on and is studied at forward EC plane, so e/pi has different results
• photon acceptance should be less than some percent level, so the current setting has problem.

### Verify Eugene baffle acceptance again after correction

After Seamus identify the needed rotation, we added those line in the baffle description perl script.

```my @offset =(-5.6, -4.4, -3.3, -2.1, -0.9, 0.1);
my \$slit_rotation = (\$i-1)*12-\$offset[\$n-1];
```

now the results look reasonable

gamma acceptance VS Mom at observer plate for full length target
electron acceptance VS Mom at observer plate for full length target
positron acceptance VS Mom at observer plate for full length target

picture ....

## Seamus's work with geant4 simulation

Reproduction of Eugene's baffles in GEMC: [1]

First attempt at a new baffle design: [2]

Other magnet baffles in GEMC: [3]

good new baffle designs in GEMC: [4]

## Eugene's work with geant3 simulation

### Eugene's procedure

```the slits were defined using the following procedure:

a) I ran GEANT simulating production in a long target,
at the edges of a phi-theta sector. The sector
width was 5 deg at thet_min and 9 deg at thet_max.
At the low phi edge (against the rotation in the field),
I took the max XBj and calculated the momentum for the given
theta. At the higher edge I took the min XBj.

b) GEANT generated hits of these tracks in the planes of the baffles.
The target length in Z makes things a bit complex, but it turned
out that simple rules could be used to select the most inner
points for the given R.
I took the hits and extrapolated the phi-R curves with parabolas
as phi=p0+p1*r+p2*r**2.
The results were stored in the PAW session.

c) Using the stored parameters of the baffles, I printed
the input to GEANT, splitting the holes in the baffles into

It was not possible to define a slit as a single shape in GEANT3.
I do not know about GEANT4. It would be a complex slice of a paraboloid,
overlapping with other volumes.
Multiple volumes work well in GEANT. One slit was defined,
then copied to all 30 sectors of the given ring. This part of the FFREAD input
code defining the geometry was generated by a script (too many lines to type
by hand).
```

### The plots in a pdf file and results in a kumac

6 plates, 30 slits per plate, 20 blocks per slit

In PVDIS PAC34 proposal, page 35 (http://hallaweb.jlab.org/collab/PAC/PAC34/PR-09-012-pvdis.pdf). It's mentioned that the baffle position is 30,60,90,120,150,180cm relative to BaBar solenoid coil center at 0. But it's actually relative to the target center which is at 10cm as seen on the Fig 3.3 on page 31.

Later on, it seems Eugene has further tweaked them to 30,58,86,114,142,170. refer to http://hallaweb.jlab.org/12GeV/SoLID/download/sim/geant3/solid_comgeant_pvdis/pvdis_02_01_p_14_01/fort.22

This requires addtional rotations of -5.6, -4.4, -3.3, -2.1, -0.9, and 0.1 degrees for plates 1-6, respectively (by Seamus)

``` macro baffle xmin=-100 xmax=100 ymin=-100 ymax=100

application data tmp.dat
3.90    5.44   176.26  183.00
5.44    6.98   176.44  182.13
6.98    8.52   176.61  181.67
8.52   10.06   176.75  181.78
10.06   11.60   176.89  181.90
11.60   13.14   177.03  182.01
13.14   14.68   177.18  182.12
14.68   16.22   177.32  182.24
16.22   17.76   177.46  182.35
17.76   19.30   177.60  182.46
19.30   20.84   177.74  182.58
20.84   22.38   177.88  182.69
22.38   23.92   178.02  182.80
23.92   25.46   178.16  182.92
25.46   27.00   178.30  183.03
27.00   28.54   178.44  183.15
28.54   30.08   178.58  183.26
30.08   31.62   178.72  183.37
31.62   33.16   178.86  183.49
33.16   34.70   179.00  183.60
tmp.dat

exec plotWedge same=[same] color=1 xmin=[xmin] xmax=[xmax] ymin=[ymin] ymax=[ymax]
* wait

application data tmp.dat
15.30   17.25   175.93  182.78
17.25   19.20   176.14  182.56
19.20   21.15   176.35  182.36
21.15   23.10   176.58  182.19
23.10   25.05   176.81  182.05
25.05   27.00   177.06  181.93
27.00   28.95   177.28  181.98
28.95   30.90   177.46  182.12
30.90   32.85   177.64  182.26
32.85   34.80   177.82  182.41
34.80   36.75   178.00  182.55
36.75   38.70   178.18  182.70
38.70   40.65   178.35  182.84
40.65   42.60   178.53  182.98
42.60   44.55   178.71  183.13
44.55   46.50   178.89  183.27
46.50   48.45   179.07  183.41
48.45   50.40   179.25  183.56
50.40   52.35   179.42  183.70
52.35   54.30   179.60  183.84
tmp.dat

exec plotWedge same=[same] color=2 xmin=[xmin] xmax=[xmax] ymin=[ymin] ymax=[ymax]
* wait

application data tmp.dat
26.60   28.96   175.71  182.49
28.96   31.32   175.95  182.40
31.32   33.68   176.20  182.32
33.68   36.04   176.46  182.27
36.04   38.40   176.73  182.23
38.40   40.76   177.02  182.22
40.76   43.12   177.31  182.22
43.12   45.48   177.62  182.23
45.48   47.84   177.93  182.28
47.84   50.20   178.15  182.46
50.20   52.56   178.36  182.63
52.56   54.92   178.58  182.81
54.92   57.28   178.80  182.98
57.28   59.64   179.01  183.16
59.64   62.00   179.23  183.33
62.00   64.36   179.45  183.51
64.36   66.72   179.67  183.68
66.72   69.08   179.88  183.85
69.08   71.44   180.10  184.03
71.44   73.80   180.32  184.21
tmp.dat

exec plotWedge same=[same] color=3 xmin=[xmin] xmax=[xmax] ymin=[ymin] ymax=[ymax]
* wait

application data tmp.dat
37.90   40.67   175.38  182.05
40.67   43.44   175.66  182.04
43.44   46.21   175.95  182.04
46.21   48.98   176.25  182.05
48.98   51.75   176.57  182.08
51.75   54.52   176.89  182.13
54.52   57.29   177.22  182.19
57.29   60.06   177.57  182.27
60.06   62.83   177.92  182.36
62.83   65.60   178.29  182.47
65.60   68.37   178.66  182.66
68.37   71.14   178.90  182.84
71.14   73.91   179.15  183.02
73.91   76.68   179.39  183.22
76.68   79.45   179.65  183.42
79.45   82.22   179.90  183.62
82.22   84.99   180.16  183.84
84.99   87.76   180.43  184.06
87.76   90.53   180.71  184.28
90.53   93.30   180.98  184.51
tmp.dat

exec plotWedge same=[same] color=4 xmin=[xmin] xmax=[xmax] ymin=[ymin] ymax=[ymax]
* wait

application data tmp.dat
49.20   52.38   175.06  181.61
52.38   55.56   175.37  181.64
55.56   58.74   175.70  181.70
58.74   61.92   176.04  181.76
61.92   65.10   176.39  181.84
65.10   68.28   176.76  181.94
68.28   71.46   177.13  182.05
71.46   74.64   177.52  182.17
74.64   77.82   177.91  182.31
77.82   81.00   178.32  182.46
81.00   84.18   178.75  182.63
84.18   87.36   179.20  182.85
87.36   90.54   179.48  183.06
90.54   93.72   179.76  183.28
93.72   96.90   180.05  183.51
96.90  100.08   180.35  183.75
100.08  103.26   180.65  183.99
103.26  106.44   180.96  184.24
106.44  109.62   181.27  184.49
109.62  112.80   181.59  184.75
tmp.dat

exec plotWedge same=[same] color=6 xmin=[xmin] xmax=[xmax] ymin=[ymin] ymax=[ymax]
* wait

application data tmp.dat
60.40   63.98   174.92  181.35
63.98   67.56   175.27  181.43
67.56   71.14   175.63  181.52
71.14   74.72   176.00  181.63
74.72   78.30   176.38  181.75
78.30   81.88   176.78  181.88
81.88   85.46   177.18  182.02
85.46   89.04   177.60  182.18
89.04   92.62   178.03  182.35
92.62   96.20   178.47  182.53
96.20   99.78   178.92  182.73
99.78  103.36   179.39  182.94
103.36  106.94   179.88  183.19
106.94  110.52   180.20  183.43
110.52  114.10   180.52  183.69
114.10  117.68   180.84  183.94
117.68  121.26   181.17  184.21
121.26  124.84   181.51  184.48
124.84  128.42   181.86  184.76
128.42  132.00   182.21  185.04
tmp.dat

exec plotWedge same=[same] color=7 xmin=[xmin] xmax=[xmax] ymin=[ymin] ymax=[ymax]

return

macro plotWedge same=' ' color=1  xmin=-100 xmax=100 ymin=-100 ymax=100

set plci [color]
if ([same] .eq. ' ') then
null [xmin] [xmax] [ymin] [ymax]
endif

DO I = 1, 30
do j = 1, 20
thmin = thmin([j])+([i]-1)*12
thmax = thmax([j])+([i]-1)*12
arc 0 0 rad([j]) rad([j]+1) [thmin] [thmax]
enddo
enddo

exec plotCompass

return

macro plotCompass offset=3 deg=12 radius=300

ndiv = 360/[deg]
message [ndiv]

angle = [offset]
do idiv = 1, [ndiv]
angle = [angle] + [deg]