Difference between revisions of "Mu Metal Shields"
| Line 1: | Line 1: | ||
| + | Updated Study (July 24, 2006) | ||
| + | |||
| + | The images below indicated that there is a 75% reduction in the gain of a Burle 8575 PMT without mu-metal shield, in the horizontal plane (at 45 and 135 degrees with respect to North) from Earth's magnetic field. There is no significant affect in the vertical direction, as expected. A thin mu-metal foil is therefore required, since Eric Scott has measured residual magnitization in the stell inserts surrounding the PMTs, as much as 3 Gauss, but more commonly around 1 Gauss. Regina will order foil in suitable rectangular sheets, which we can then roll and tape and insert around the PMT. | ||
| + | |||
| + | [[Image:Par-With.jpg]] | ||
| + | |||
| + | [[Image:Par-Without.jpg]] | ||
| + | |||
| + | [[Image:Perp-With.jpg]] | ||
| + | |||
| + | [[Image:Perp-Without.jpg]] | ||
| + | |||
| + | [[Image:Vert-With.jpg]] | ||
| + | |||
| + | [[Image:Vert-Without.jpg]] | ||
| + | |||
| + | ----- | ||
| + | |||
Scope traces of a Burle 8575 PMT attached to a small Nai crystal with an embedded 241Am source, taken with and without its mu-metal shield. A small gain difference appears that will be investigated further. | Scope traces of a Burle 8575 PMT attached to a small Nai crystal with an embedded 241Am source, taken with and without its mu-metal shield. A small gain difference appears that will be investigated further. | ||
[[Image:mumetal-yes.jpg]] [[Image:mumetal-no.jpg]] | [[Image:mumetal-yes.jpg]] [[Image:mumetal-no.jpg]] | ||
Revision as of 18:57, 24 July 2006
Updated Study (July 24, 2006)
The images below indicated that there is a 75% reduction in the gain of a Burle 8575 PMT without mu-metal shield, in the horizontal plane (at 45 and 135 degrees with respect to North) from Earth's magnetic field. There is no significant affect in the vertical direction, as expected. A thin mu-metal foil is therefore required, since Eric Scott has measured residual magnitization in the stell inserts surrounding the PMTs, as much as 3 Gauss, but more commonly around 1 Gauss. Regina will order foil in suitable rectangular sheets, which we can then roll and tape and insert around the PMT.
Scope traces of a Burle 8575 PMT attached to a small Nai crystal with an embedded 241Am source, taken with and without its mu-metal shield. A small gain difference appears that will be investigated further.
