1. 1Beam Line Review. 17th November 2007

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4. 4 Detector parameters Fermilab Beam line monitors built to replaced SWICS Scintillating fibre tracker – readout by multi-anode PMTs Channel count is 64 (per view) Fibres may be spaced apart or arranged touching Range of fibre thicknesses possible and reading more than 1 fibre out per anode. Thinner means higher resolution Thicker means more light

5. 5Beam Line Review. 17th November 2007 Design decisions 1 mm was chosen as a suitable thickness to produce enough light. 1mm readout pitch will only produce a detector 64mm across. The choice is 1mm with gaps No gaps and more than 1 fibre per anode The ability to measure the total integrated flux in the beam guides us to the multi fibre option

6. 6Beam Line Review. 17th November 2007 Monitor dimensions and pitch UPSTREAM MONITOR For the upstream monitor grouping in sets of 3mm gives a total size of 192mm Compared with the specification of 200mm. A fit to a distribution with 3mm pitch will give a resolution of the mean to better than 1mm as required for beam based alignment. DOWNSTREAM MONITOR For the downstream monitor grouping in sets of 8mm gives a total size of 512mm Compared with the specification of 472mm. Fitting this will provide a resolution of around 2mm. This is sufficient for the steering of the beam, but is not good enough for beam based alignment which needs 1mm. Central area 48mm x 48mm at a pitch of 3mm and the rest at a pitch of 8mm. Total size 432*432mm. Meets beam based alignment requirements for central region and around half the resolution over the rest of the area

7. 7Beam Line Review. 17th November 2007 Readout UPSTREAM MONITOR Discriminate and count. Read out scalers once per spill. If rates too high, go over to integrate and digitise: changing PMT HV gives a way of tuning sensitivity or allowing for PMT saturation. DOWNSTREAM MONITOR Discriminate and count. Read out scalers once per spill. Result is a beam shape, but no particle by particle information – moving the gate would provide a way of measuring time dependant effects if required Rates with beam but no target are negligible

8. 8Beam Line Review. 17th November 2007 Monitor drawing

9. 9Beam Line Review. 17th November 2007 Background problems The beam may be bigger than the area of the detector Fibres running from the “sensitive” area to the PMT are exposed to beam. Create simple model of smooth beam with independent x and y distributions, and PMTs in the centre. Fibre runs simplified (lengthened) Compare “true” v “measured” for beams of various widths, both gaussian and top hat (modelled as wide gaussian). No reliable model of shape in the wings

10. 10Beam Line Review. 17th November 2007 Beam Monitors sigmaVert=30 sigmaHoriz=30 : Beam Uniform, Larger than chambers sigmaVert=10 sigmaHoriz=10 : Beam Contained Beams which overhang the edge are measured poorly in terms of width and centroid, but they are poorly defined. Beams which are well defined are only marginally affected. Corrections are possible. Inconvenienced but not spoiled

11. 11Beam Line Review. 17th November 2007 Cable Runs Cable run