  |
X-Ray Polarimetry Workshop SLAC, Stanford, California 9-11 February 2004 |
| NASA Site Home | | SLAC Site Home | | Talks on the Web | | Poster (PDF) | |
X-ray Polarimeter using Optical Imaging Capillary Gas Proportional Counter
Hirohisa
Sakurai
Dept. of Physics
sakurai@sci.kj.yamagata-u.ac.jp
H. Sakurai, F. Tokanai, S. Gunji
An image of a photoelectron track is one of the most important tools for X-ray polarimetry, since the ejected directions of photoelectrons produced by polarized X-rays are distributed with an angular distribution around the electric vector of X-ray polarization. Accordingly, X-ray polarization can be measured by the detection of a fine image of a photoelectron track. In X-ray astronomy, if we have a good focal plane X-ray polarimeter, the development of focusing mirrors allows the observation of X-ray polarization of approximately 1%. In the energy range from a few keV to a few tens of keV, the X-ray polarimeter with a fine pixel gaseous detector is advantageous because the pixel detector simultaneously has the capability of fine position determination for incident X-ray as well as imaging of a photoelectron track. We have been developing an optical imaging capillary gas proportional counter (CGPC) as a microsegmented pixel detector. The light signal from each capillary is read out as an imaging signal using an image-intensified CCD camera combined with the CGPC through a lens optical system. As the light emission region is confined in the capillary, the segmentation of the signals is very fine with little signal crosstalk. To investigate the performance of the optical imaging CGPC as the X-ray polarimeter, we have used polarized X-rays in the synchrotron facilities SPring-8 and KEK-PF. Because the polarized X-ray has a highly polarized beam with high intensity for monochromatic X-ray energy, it is well suited for investigating the characteristics of the polarimeter. For the polarized X-rays in the energies of 10, 15, and 20 keV, the angular distributions were derived from the images of photoelectron tracks. The modulation factor was 25.1Å}2.0% for the X-rays with a polarization degree of 99%. We will describe the images of single photoelectron tracks, the directions of photoelectrons, and the performance of the optical CGPC as a polarimeter in detail.
|
For more information, contact
Jennifer Formichelli |
||
 |
 |
|