Pion Beta Cosmic Veto Counter

You will find the originally designed Cosmic Veto technical drawing on The Detector Handbook Page. Some small modifications have been necessary. The design of the top part of the CV counter is finished. Here you'll find the technical drawing for this detector part:

CV Top drawing

We are using scintillator material from counters which are not in use now. The next figure shows one of these counters after opening the cover:

Old CV Counter

The available scintillator material and the final assembly of this pieces to our CV counter is shown in the next figure:

Size of Scintillators

For the design of the side walls it is necessary to try to get the whole detector as tight as possible - especially to cover the non-active parts (metal frame and wavelength shifter) by an overlap of the edges. Here you'll see the alignment of the top to the side walls (view from beam side) :

Overlap Frontview

  Here you will see a side view of the Cosmic Veto overlap. The beam comes in from the left:

Overlap Sideview

The whole counters are covered by solid steel plates. It's impossible to get these plates of this size in one piece. So we have to produce it from standard plates of 3000 mm x 1500 mm size:

Size of Steel Plates

The counters will be read out on each of the four corners of a plane. On the top edges we have the readouts of 3 sides together.
One problem will be the choice of the photomultiplier tubes. The use of XP2020 will cause some trouble, because the space is very limited. The next two sketches will show the projections of these edges for the use of XP2020 tubes.

Edge Of The Top Front Projection (beam view) of the CV House edge top left

Side Projection CV Top   Side projection of the CV House

An alternative woulde be the use of 1'' HAMAMATSU 5600 PMTs, which are in use for the Plastic Veto Counter. The wavelength shifters can be cut to fit the active area of the phototube:

Cutting of the WLS:

Cutting The WLS      Cutting The WLS

One relevant for the choice of the scintillator material is the attenuation length. The first results for measuring this parameter you will find on Test Setup Page

Here you will find the dimensions for the scintillator plates we want to order:
CV Scintillator Material

Here we have three pictures from the CV detector assembly:

CV AssemblyCV AssemblyCV Assembly

On the next two pictures you can see signals from the CV counter, taken with an TEKTRONIX TDS 744 digital scope:

CV Signal CV signal, externally 



Quality Control for the scintillator material

Test for the rectangular readout for Cosmic Veto F/B counters

The Cosmic Veto House Sidewalls

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H.P. Wirtz , 04-Mar-1999
last update:  14-Apr-2000

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