Photon Factory Activity Report 2004 #22 Part B (2005)
Instrumentation and Technique

11A/2004G214

X-ray Polarimeter with Transmission Multi-layers
Shunji KITAMOTO*1, Norimasa YAMAMOTO1, Junichi KANAI1,Yohei OHKAWA1, Shigeto
CHIBA1, Keisuke SUDOH1, Junichi SATOH1, Takeshi WATANABE1, Kazuharu SUGA1, Takayoshi
KOHMURA1, Hideyo KUNIEDA2, Yoshitomo MAEDA2, Shunsaku OKADA2, Ryo IIZUKA2,2
2Akiharu ITOH , Yumi ITOH
1
Rikkyo University, 3-34-1, Nishi-Ikebukuro, Toshima-ku, Tokyo, 171-8501, Japan
2
ISAS/JAXA, 3-1-1, Yoshinodai, Sagamihara, Kanagawa, 229-8510, Japan
Introduction
The polarization of the X-ray from astronomical
objects includes important information of the X-ray
emission mechanism and sometimes of the geometricalsituation of the X-ray sources. However, since themeasurement of the X-ray polarization is relatively
difficult, the significant observation has not been
performed so far, except for some bright sources. One
reason is that the complex mechanism for the polarization
measurement is not suitable for the detector which must
be installed onboard the satellite.
The reflectivity and the transmission of the Multi
Layers depend on the polarization, especially for the 45
deg incident angle. The transmission type polarimeterhas been developed by Yamamoto(1993).
Thetransmission type polarimeter might be very suitable forthe detector onboard the satellite, because thetransmission polarimeter can be used as a filter, which
can be install in front of the other conventional detectors.
If the detector is an imaging detector, such as a CCD, theimages as a function of the position angle of thepolarization can be observed. This would give us
unprecedented information of the astronomical objects.
We started the investigation of the transmission typepolarimater with multi layers.
Multi Layers
The transmission of the multi layers are calculated
according to Underwood and Barbee (1981). Considering
the technical feasibility, we now chose a Mo/Si multilayers for 13.5nm wave length. This is not well suitable
for the astronomical usage, but is suitable for the testdevelopment. A Si3N4 thin film is used as a substrate.
The thickness is 100nm and its size is 1mm square. The
simulated transmission is shown in figure 1. The ninelayer pare is optimum with high transmission and big
difference between S- and P- polarization. The multilayers were fabricated by a DC magnetron spattering at
JAXA/ISAS.
Performance Evaluation
The photons around 13.5nm were exposed onto theMo/Si multi-layers on the Si3N4 substrate with theincident angle of 45 deg using the BL11A beam line. The
transmitted photons were detected by a photo-diode. The
multilayer can be rotated around the axis on the beam line.

The photon energy was scanned from 12.5nm to 14.5nm,
The measurements have been performed at the sevenposition angles from -90 deg to 90 deg with 30deg step.
The measured transmissions are compiled in the figure 2.
The clear performance for the polarimater has been
confirmed.
References[1] M. Yamamoto, OYO Butsuri, 62, 676-682 (1993)[2] J.H. Underwood and T.W. Barbee, Jr. Applied Optics
20, 3027-3034 (1981).
*kitamoto@rikkyo.ne.jp

Figure 1. The transmission of Mo/Si multi-layers on
a 100nm Si3N4 substrate for S and P polarization,respectively. The incident angle is fixed at 45 deg.

Figure 2. The measured transmission of themulti-layers around 13.5nm region, for four
position angles, -90, -60, -30 and 0 deg.
Thetransmissions at 84eV are normalized to be 1.

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