Ⅱ-7. Astrophysics and Astro-Glaciology
RIKEN
Accel. Prog. Rep. 56 (2023)

RIKEN Accel. Prog. Rep. 56 (2023)

Demonstration of multiplexing lobster-eye optics
Y. Zhou,∗1,∗3 T. Mihara,∗1,∗2 T. Tamagawa,∗1,∗2,∗3 and K. Uchiyama∗1,∗3
Wide-ﬁeld X-ray monitor is essential in astronomy tocatch short-time events, such as gamma-ray bursts,1)
and neutron-star mergers.2) The all-sky X-ray monitor,
MAXI,3) which we have operated on the ISS since 2009,
has proven its usefulness. As an extension of MAXI tothe soft X-ray band and precise-imaging, we introduced
the multiplexing lobster-eye (MuLE) optics.4) we haverecently performed veriﬁcation experiments of MuLEfor the ﬁrst time. In this report, we present the angularresolution of MuLE obtained with Ti Kα (4.5 keV) Xrays.
The test setup is shown in Fig. 1. We used microporous optics (MPOs) made by NNVT company with
R = 750 mm and the size of 43 mm square. The CMOS
image sensor was Gpixel 400BSI-TVISB, whose size was
22.5 mm square. X-rays through the three MPOs focuson a single CMOS placed on the focal plane at a radiusof R/2, where R was the curvature of MPO. The ﬁeldof-view of a mirror is 3 deg × ±1.5 deg. Each mirror
was centered at 0 deg, 9 deg and 18 deg like steppingstones. We added the other side at −9 deg and −18 deg
to make one unit. Using 3 units, the whole ±20 deg ×±1.5 deg sky can be covered. This CMOS has a goodenergy resolution. We measured the energy resolutionof the CMOS for Ti Kα to be ∆E/E = 3.7% (FWHM)
with single-pixel events at room temperature.

3.85 m. The focal length was measured as 345 mm forthis diverging light. In our experiment, the CMOS wasset in this distance. Focal length for the parallel light
was calculated to be 379 mm. It is close to the designed
value (375 mm).
2 MPOs were placed on a mount, and measured Seg-0
and Seg-1 ﬁrst. The Seg-0 mirror was rotated clockwisearound the optical axis by 10 deg, while Seg-1 was 0 deg
upright. The direction of the cross arm identiﬁes theMPO which the X-ray comes from. After we measured
Seg-0 and Seg-1 we moved the whole mount so that theSeg-1 MPO can locate Seg-2. Then we measured Seg2. Although Seg-1 and Seg-2 are the same MPO, theimage of the Seg-2 was rotated anticlockwise by 10 deg
in Fig. 1 for understanding.
A demerit of the MuLE is that the CMOS is placedin a slanted way for the Seg-1 and Seg-2, which makes
the image worse in the X direction in our setting.
By ﬁtting the peak of the core in the image, the widthof the focus can be measured. The angular resolution(σ) was shown in Fig. 2. It distributed between 4 arcmin to 8 arcmin, which is acceptable. Some jumping
data points are due to irregularities on the LE surface.

Fig. 2. Incident X-ray angle and position resolution (σ).

Fig. 1. MuLE experiment and X-ray images of three LE.
The brightness corresponds to X-ray intensity.

We showed the focus images in Fig. 1 right. The
distance of the Ti X-ray generator to the MPO was
∗1
∗2
∗3

RIKEN Nishina Center
High Energy Astrophysics Laboratory, RIKEN Cluster forPioneering Research
Department of Physics, Tokyo University of Science- 63 -This report demonstrated the MuLE system worked
as expected. MuLE system can be used in small satellites or ISS payloads to compensate for the soft X-ray
performance of MAXI.
References
1) R. Vanderspek et al., Astrophy. J. 617, 1251 (2004).
2) B. P. Abbott et al., Phys. Rev. Lett. 119, 161101 (2017).
3) M. Matsuoka et al., Publ. Astron. Soc. J. 61, 999 (2009).
4) T. Tamagawa et al., J. Astron. Telesc. Instrum. Syst. 6,025003 (2020).