Primex Photon Beam Stabilityat HyCal

Waightstill W. AveryNC A&T

July 11, 2008

Purpose

Determine the photon beam positions and resulting stability during the experimental run at HyCal using EPICS data

DefinitionsBPM – Beam Position Monitor

( permanent hall-B BPM 2C24A )HyCal – Hybrid Shower Calorimeter

Pb Glass PBWO4 crystals

PGP – Primex Gamma Profiler

All devices are assumed to be in the same frame of reference, with HyCal requiring an initial offset that was acquired from a survey

The angles ( x, y, z) are measured from their respective positive axes

ProcessThree databases were used for data extraction

using MySQL protocols ncat2.jlab.org/beamOrientation primexdb.jlab.org/book_keeping ncat3.jlab.org/test

112 runs (used in Ilya’s 0 analysis ), dubbed “Gold”, “Silver” and “Empty Target” runs, were used to extract EPICS data from these databases

For every EPICS event within individual runs the x and y-coordinates were retrieved for both the BPM and the PGP

Assuming that no magnetic field exists between the BPM and HyCal, parametric equations for a straight line trajectory were created to give the transverse coordinates on the face of HyCal relative to the BPM and PGP

Calculating Angles at HyCal

The law of cosines was used as a test to verify that our angle calculations were valid and returned a value of one for each EPICS event

Subtracting the angle from 90-degrees shows the deviation in each direction from the initial beam trajectory

’X/Y = /2 - X/Y

Golden Beam Tune - Run 4349

Removal of Beam-Trips

Removal of Beam-Trips

SummaryAfter the Golden Tune of the photon beam

was established, beam-trips were removed using JuLeia’s live time analysis

The beam position variations were well within HyCal resolution ( 1.3 mm)

The database was updated with the newly calculated x & y-coordinates of the beam at HyCal, as well as the x, y, and z angular deviations for each EPICS event for each run

The acquired information can be used to correct 0 trajectory

The updated data is available for collaboration-wide use