Introduction

This page is meant to collect documents and information used as input to the constants used in the geometry of the HPS software for the Test run.

Documentation

#1: Ecal dimensions and channel mapping, 3D model of ECal enclosure
#2: vacuum chamber position
#3: vacuum chamber details
#4: ecal alignment position 
 

Definitions

• z is in beam direction and z=0 is defined as our nominal target position.

Alignment constants

B-field - represented as a "box"

Distance in z from our nominal target to the center of the analyzing magnet. 
From #2, page 2: Length of dipole magnet is 36"=91.44cm with upstream face at z=0.

        <constant name="dipoleMagnetPositionZ" value="45.72*cm"/>

Length of magnetic field in z.
Using fringe field measurement to define the half-field point in the x=y=0 line along z.  

        <constant name="dipoleMagnetLength" value="108*cm"/>       

From #3:

        <constant name="dipoleMagnetHeight" value="17.78*cm"/>
        <constant name="dipoleMagnetWidth" value="41.6052*cm"/>

Ecal position

From #2: distance from flange to downstream edge of the dipole magnet: 401.6mm
From #4: distance from flange to crystal face is 154mm.

The distance from crystal face to nominal target position z=0 is therefore 401.6mm+154mm+914.4mm = 1470mm
Detectors have been using 152.4cm for a while. Need to correct.  

From Stepan: surveyed distance between ecal halves was 40+-2mm
From #4: distance between fiducially and innermost face of crystal is designed to be 17+-1mm.

The distance between the beam plane (y=0) and innermost crystal face is there for (40+17*2)/2 = 37mm. 

            <layout beamgap="37.0*mm" nx="46" ny="5" dface="152.4*cm">

Converter position

From #1, page 1: 44.53"=113.11cm from the converter to the center of the magnet. 
From #2, length of maget is 91.44cm with upstream face at z=0.

The converter position w.r.t. z=0 i.e. our nominal target position, is therefore 91.44/2-113.11mm = -67.39cm and w.r.t. to the face of the ecal crystals 1470+673.9mm = 2143.9mm