MVD FMDR - MVD thickness

MVD CURRENT MASS BUDGET

Description	Material	Radiation Length
Inner Enclosure Wall	0.01mm Al 2 mil adhesive 3mm Rohacell 2 mil adhesive 0.01mm Al	0.014 % 0.017 % 0.055 % 0.017 % 0.014 %
Inner Silicon Layer	0.3mm Si	0.321 %
Rohacell Cage (*)	24.4mm Rohacell x average mass ratio	0.109 %
Outer Silicon Layer	0.3mm Si	0.321 %
Kapton Cable	0.05mm Kapton 0.005mm Cu (x .5 area) 0.005mm Cu (x .1 area)	0.020 % 0.018 % 0.004 %
Outer Enclosure Wall	0.01mm Al 2 mil adhesive 6mm Rohacell 2 mil adhesive 0.01mm Al	0.014 % 0.017 % 0.110 % 0.017 % 0.014 %
.	Grand totals for 1 layer of Silicon for 2 layers of Silicon	. 0.76 % 1.08 %

(*) The radiation length for Rohacell 71 is 545cm. The Rohacell cage weighs 3.05g, and parylene coating adds 45%, for a total of 4.4g. A solid block of Rohacell of the same outside shape weighs 18g. The distance between the inner and outer Silicon detectors is 2.44cm. (2.44cm/545cm)*(4.4g/18g)*100%=0.109%

To set the scale,

a Beryllium beam pipe would be 0.28%
the 'Dalitz Decay Equivalent' would be 1.54%
2m of air is 0.66%

for a total irreducable amount of about 2.46%. The MVD would increase this by 1/3 to 1/2.


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last update 25 July 97 - Hubert van Hecke