The table below was prepared by Marat, October 27, 1999
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Rate estimates
Assume that density = 0.090 g/cm3 , d_omega = 6.7 msr, dz = 5.8cm*
horizontal acceptance = -28.7 mr to 28.7 mr, the extra width reflects
the use of an extended target
vertical acceptance = -60 mr to 60 mr , m(3He) = 4.9817e-24g
rate = (dQ/dt)/e*(rho*dz)/m(3He)*(sig-av)*d_omega
commissioning period in December 1999, table prepared by Marat Rvachev,
10/27/99
Elastic Scattering Rates
Date E
Theta(deg) sig-pt
sig-avg rate@ 1uA** Time(@20uA)***
Q2
MeV deg
fm2/sr fm2/sr
sec -1
hours
fm2
12/99 845 12.54
7.61e-3 7.85e-3
344K
0.23#
0.870 Use as much
of the commissioning time
845 16.54
1.30e-3 1.35e-3
59.1K
0.23#
1.50
as possible to measure these elastic
845 19.15
4.44e-4 4.60e-4
20.1K
0.23#
2.00
cross sections. This will give us
845 30.94
4.89e-6 5.08e-6
222
0.23#
5.01 information
right at the start of the
845 45.20
3.82e-8 3.95e-8
1.73
0.35
9.96 data taking
as to how well we can
845 67.87
3.26e-10 3.29e-10
0.0144 14.3
19.27 independently determine
cross sections.
845 86.57
2.74e-11 2.75e-11
1.21e-3 170.
26.91
* This length along the beam assumes that the spectrometer views the
10 cm target at 12.5 deg, and thus the ytg view is 21.6 mm across.
Given a transverse position resolution of 1.5mm ( from WWW) and requiring
3 sigma separation between the wall and the beginning of the
ytg cut means -6.3mm<ytg<6.3mm. This produces a usable length
along the z direction of ztg= ytg/sin(12.5deg) = 58 mm.
** These are the rates for the data of interest, i.e., with the cuts as described. The total elastic rate into the spectrometer will be larger since the spectrometer sees the full target length at some angles.
*** Assumes we collect 15000 elastic events.
# nominal time, not rate limited
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Detailed Run Plan
activity delta time total time
1) ARC energy measurement 4 hrs 4 hrs
2) BCM, current monitor calibration
1hr
5hrs
3) optics study, C elastic settings, Nilanga, theta_e = 16.54
deg
8 hrs
13 hrs
P_e = 0.8429, P_h=0.8429, theta_h=16.54deg
both HRSE and HRSH set for electrons
4) move HRSH to theta_h = 30.94 deg, P_h = 0.8108 Gev/c
1 hr
14 hrs
HRSH will serve as a luminosity monitor
for the rest of
commissioning . This is the Q2
= 5.01 /fm2 for elastic scattering
and the rates should exceed about 30K
in HRSH for any beam current .
change momentum of HRSE to
P_e = 0.8351 .
5) 3He(e,e), theta_e=16.54 deg, I_e = 2uA
.23 hr
14.23 hrs
P_e = 0.8351 , Q2
= 1.50 /fm2
6) change HRSE angle to 19.15 deg
.27 hr
14.5 hrs
change HRSE momentum to P_e =
0.8317
7) 3He(e,e), theta_e= 19.15deg, I_e = 5 uA
.23 hr
14.73 hrs
P_e = 0.8317
, Q2 = 2.00 /fm2
8) change HRSE angle to 30.94 deg
change HRSE momentum to P_e =
0.8108
.27 hr
15 hrs
9) I scan and 3He(e,e), theta_e= 30.94 deg
P_e = 0.8108 , Q2 = 5.01
/fm2, spectrometer rates
should not be excessive at this Q2
I = 1uA
.25 hrs
15.25 hrs
I = 2 uA
.25 hrs
15.5 hrs
I = 5 uA
.25 hrs
15.75 hrs
I = 10 uA
.25 hrs
16.0 hrs
I= 20 uA
.25 hrs
16.25 hrs
I = 40 uA
.25 hrs
16.50 hrs
I = 60 uA
.25 hrs
16.75 hrs
I= 80 uA
.25 hrs
17. hrs
I = 100 uA , HRSE rate about 30K
.25 hrs
17.25 hrs
10) change HRSE angle to 45.20 deg
.5 hr
17.75 hrs
change HRSE momentum to P_e =
0.7765
11) 3He(e,e), theta_e= 45.20 deg, I_e = 10 uA
.5 hr
18.75 hrs
P_e = 0.7765 , Q2
= 5.01 /fm2
12) change HRSE angle to 67.87 deg
.5 hr
19.25 hrs
change HRSE momentum to P_e =
0.7120
13) 3He(e,e), theta_e= 67.87 deg, I_e = 60 uA
5 hrs
24.25 hrs
P_e = 0.7120,
Q2 = 19.27 /fm2
(Note: We should not do the Q2 = 26.91 /fm2 elastic scattering point at this energy. It would require 34 hrs at 100 uA. This will have to wait until March.)
14) change HRSE angle to theta_e= 30.94 deg
.5 hr
25.75 hrs
change HRSE momentum to
P_e = 0.8108
this is back to the Q2 = 5.01
fm/2 point
15) raster size scan ( M. Kuss) trs 25.75+trs
16) beam displacement scan at Q2 = 5.01 /fm2, I_e
= 1 uA
turn raster off
vertical + 1mm , horizontal
0mm
.25 hrs
26 +trs
vertical - 1mm, horizontal
0mm
.25 hrs
26.25 + trs
vertical 0 mm, horizontal
+1mm
.25 hrs
26.50 + trs
vertical 0mm, horizontal
-1 mm
.25 hrs
26.75 + trs
17) fan scan ( M. Kuss) tfs 26.75+trs+tfs
18) change density of target to 1/2 2 hrs 28.5 + trs +tfs
19) 3He(e,e), theta_e= 30.94 deg, measure elastic at 1/2 density
0.5 hrs
29+trs+tfs
P_e = 0.8108 , Q2
= 5.01 /fm2, I_e = 10uA
this also checks the
simulations for the resolution