Re: Detector mass questions

From: Jonathan Link <>
Date: Wed Aug 04 2004 - 10:26:27 CDT

Hi Hans,

To me there are two factors which will help to determine the size and
shape of the detector. First, what is the actual shaft opening size and
second how much weight can we lift. Both of these may have very real
cost incentives to go smaller. Clearly if lift capability is cheep and
shaft diameter is expensive then we will want to carefully examine the
possibility of a cylindrical detector. There are several issues:

1) Can we move upright cylindrical detector of 250 tons and10 meters
high, horizontally across the surface and if so what are the costs
associated with this?

2) What is the attenuation length of the target material, and what is
the maximum direct pathlength for light that is acceptable?

3) Are there physics advantages to multiple small detectors?
Independently measured relative efficiencies allow you to combine
measurements from different detectors and improve the effective relative
efficiency error by 1/sqrt(n).

4) There are some unexpected factors to keep in mind such as having to
pass a large metallic object under the high voltage lines coming off the
plant. The Braidwood engineers expressed some concerns about a 6 meter
tall detector. What are the real safty limits?


Hans Jostlein wrote:

> Hi, Jonathan, Ang Lee pointed out that the detector mass is not 200
> ton, but quite a bit less. I have calculated the mass for a 6.8 m
> diameter sphere , filled with mineral oil, made of 1/4 inch steel.I
> get 147 (metric) ton total.Supports and electronics may pop this up
> to about 150 ton, but not much more. I think we need to be careful not
> to add safety factors at every stage.Things can get funky
> quickly! Hans____________________________________________________________________________By
> the way, if the borehole cost dominates (as I suspect), it may be
> worth looking at slightly non-spherical shapes.I have done a paper
> exercise of adding a cylindrical section equal to one radius (3.4 m)
> to the vessel.As one might expect the mass goes up (from 147 ton to
> 256 ton),accompanied by a large gain in fiducial volume, from 24.5 m^3
> to 55 m^3, more than double.It may be worth running the light
> collection Monte Carlo for this shape.The gain ratio will be available
> at any diameter.We may be able to do a better experiment, reduce cost,
> or
> both Hans _________________________________________________________________________________
  Pi 3.141593
  diameter 6.8 m
  Volume 164.6362 m^3
  Density of oil 850 kg/m^3
  Oil Mass 139940.8 kg 139.9408 ton

  Surface area 145.2672 m^2
  Steel thickness 6.35E-03 m
  Steel density 7850 kg/m^3
  Steel volume 9.22E-01 m^3
  Steel mass 7.24E+03 kg 7.241209 ton

  Fiducial volume
  diameter 3.5 m
  Fiducial volume 22.4493 m^3

  Total mass 1.47E+05 kg 147.182 ton

  Add cylinder of height one

  Added height 3.4 m
  Added volume 123.4772 m^3
  Added mass 104955.6 kg
  Added surface area 72.63362 m^2
  Added steel volume 4.61E-01 m^3
  Added steel mass 3.62E+03 kg

  Total added mass 1.09E+05 kg 108.5762 ton

  Fiducial volume
  diameter 3.5 m
  Added Fiducial volume 32.71183 m^3

  Total new mass 2.56E+05 kg 255.7582 ton

  Total new fiducial
  volume 55.16113 m^3
Received on Wed Aug 4 10:26:29 2004

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