Hi,
Karen, Jim, and I have made some rough measurements of the BLAST
magnetic field. The attached file provides the measurements for your
perusal and comments.
I will convert the measurement coordinates into BLAST
coordinates and compare the measured field with that used in
reconstruction and send another message.
But for now the observation is that at the inner, entrance
window of the wire chambers the right sector has higher field than
the left (on the order of a few percent) while on the outer, exit
window of the wire chambers the right sector is lower than the left
(again by a few percent). This could be simply explained by the right
sector being further from, and the left being closer to, the central
axis of the magnetic field which is consistent with Karen's survey
which shows a shift to the right from previous measurements.
Another test where we measured the field in the left sector with
the sub-detector opened and closed is also provided. The results on
the struts which are close to the tracking region, but at an
azimuthal angle of -20 degrees or so, shows negligible. There is a
strong effect near the edge of the frame. But note that this area is
actually quite far from the tracking region and is close to the
actual shielding so could be expected to be sensitive.
Cheers,
Douglas
26-415
M.I.T. Tel:
+1 (617) 258-7199
77 Massachusetts Avenue Fax: +1
(617) 258-5440
Cambridge, MA 02139, USA E-mail:
hasell@mit.edu
This archive was generated by hypermail 2.1.2 : Mon Feb 24 2014 - 14:07:32 EST