Difference between revisions of "Material specifications for FDC Redesign"
From GlueXWiki
| Line 1: | Line 1: | ||
We are pursuing a couple of options for reducing the thickness of the FDC packages. The following items are common to both designs: | We are pursuing a couple of options for reducing the thickness of the FDC packages. The following items are common to both designs: | ||
| + | |||
| + | * The anode wires are tungsten 20 microns in diameter. The gold plating is a negligible contribution to the mass of the wire. | ||
| + | |||
| + | * On either side of an anode sense wire is a field wire. The field wires are aluminum with a diameter of 100 microns. | ||
| + | |||
| + | * On either side of the anode planes are cathode planes composed of copper deposited on Kapton. | ||
* The thickness of the Kapton in each cathode plane is 25 microns. | * The thickness of the Kapton in each cathode plane is 25 microns. | ||
| Line 5: | Line 11: | ||
* The thickness of the Copper in each cathode plane is 2 microns. | * The thickness of the Copper in each cathode plane is 2 microns. | ||
| − | * The strips are excluded from a 10 cm diameter region about the beam line. | + | * The copper strips are excluded from a 10 cm diameter region about the beam line. |
* There is one ground plane between each set of cathode planes and on the upstream and downstream face of each chamber package composed of 6.3 micron Mylar with 0.1 micron Aluminimum on each side of the Mylar. | * There is one ground plane between each set of cathode planes and on the upstream and downstream face of each chamber package composed of 6.3 micron Mylar with 0.1 micron Aluminimum on each side of the Mylar. | ||
Revision as of 17:56, 12 June 2007
We are pursuing a couple of options for reducing the thickness of the FDC packages. The following items are common to both designs:
- The anode wires are tungsten 20 microns in diameter. The gold plating is a negligible contribution to the mass of the wire.
- On either side of an anode sense wire is a field wire. The field wires are aluminum with a diameter of 100 microns.
- On either side of the anode planes are cathode planes composed of copper deposited on Kapton.
- The thickness of the Kapton in each cathode plane is 25 microns.
- The thickness of the Copper in each cathode plane is 2 microns.
- The copper strips are excluded from a 10 cm diameter region about the beam line.
- There is one ground plane between each set of cathode planes and on the upstream and downstream face of each chamber package composed of 6.3 micron Mylar with 0.1 micron Aluminimum on each side of the Mylar.
- The FDC frames in the inactive area are composed of a composite E-glass/carbon fiber/rohacell sandwich, polyethylene spacers, and G10 wire frames as described
in GlueX-doc-800.
- The chamber gas mixure is 40% Argon/60% CO2.
The two options for the rest of the material are:
- Option 1: 5 mm thick low-density Rohacell backing in the active region associated with each cathode plane with a 10 cm diameter hole cut out of the center (including the copper and Kapton).
- Option 2: No foam backing in active region, but the Kapton goes all the way through the beam hole.
The questions we would like to address are:
- What is the effect of reducing the material in the inactive area on photon conversions? Does the design option of replacing the G10 cathode frames with the
carbon fiber composite meet our physics requirements for the level of photon conversions? Do we also need to consider replacing the polyethylene spacers with the carbon fiber composite design?
- What is the effect of reducing the material in the active area on rates on the strips and wires near the beam line? Does this thickness meet our design requirements for momentum resolution vs. momentum and angle?
The crucial goal here is to set final specifications for the material thickness in the inactive and active portions of the FDC system so that the design can proceed.
