Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 51 (2018)

Delay-line Anode for MCP-based Position Sensitive Detector
at Rare RI Ringelectrons

mask for calibration

MCP-2400V

Fig. 1. Principle of the MCP with 2-D delay line anode;
the MCP was placed in vacuum (3.5 × 10−3 Pa).
∗1
∗2
∗3
∗4
∗5
∗6RIKEN Nishina Center, RIKEN
Institute of Modern Physics, Chinese Academy of Sciences
School of Nuclear Science and Technology, Lanzhou University
University of Chinese Academy of Sciences
Department of Physics, Saitama University
Institute of Physics,University of Tsukuba- 153 -I(a)40200accuracy (mm)60y(mm)Rare RI Ring1) (R3) is a newly developed mass spectrometer for the measurement of exotic nuclei with ahigh precision of 10−6 . In order to achieve this goal,
beam diagnostics need to be on the beam line (including BigRIPS, SHARAQ, and R3 injection)1) for several reasons: (1) velocity measurement with a precision of 10−4 is needed for mass determination;2) (2)in order to improve the transport eﬃciency, emittancematching should be applied, which requires emittancemeasurement before the ring.3,4) To achieve a precision of 10−4 for the velocity measurement, new position sensitive detectors with energy loss as low as 10−5
are needed, which cannot be achieved by conventional
PPAC. High position resolution (< 1 mm) and high efﬁciency (∼100%) are also needed. For these detectors,
it is very important to use position sensitive anodes
for collecting the secondary electrons. To achieve highposition resolution, we chose 2D delay-line anode forMicro-Channel-Plate (MCP) based detectors. The result of the calibration and position resolution of theanode is shown in this report.
A mask with several holes (the size of the holes were1 mm and 0.5 mm in diameter) was placed on theMCP, whose active area had a diameter of 120 mm,
as illustrated in Fig. 1. We used the vacuum gauge as

2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5

accuracy (mm)H. F. Li,∗1,∗2,∗3,∗4 Z. Ge,∗1,∗5 S. Naimi,∗1 D. Nagae,∗1 Y. Abe,∗1 T. Uesaka,∗1 T. Yamaguchi,∗1,∗5,∗6 F. Suzaki,∗1Y. Yamaguchi,∗1 M. Wakasugi,∗1 S. Omika, ∗1,∗5 K. Wakayama,∗5 H. Arakawa,∗5 A. Ozawa,∗1,∗6 S. Suzuki,∗1,∗6and T. Moriguchi∗1,∗62.0
1.5
1.0
0.5
0.0-0.5-1.0-1.5

II-20-40-60-60 -40 -20 0-20x(mm)4060-

linear function(b)quadratic function

-40

-20

linear function

0y(mm)

20(c)quadratic function-40-20400x(mm)2040

Fig. 2. (a) Image produced by the electrons that passthrough the mask’s holes and hit the MCP; (b), (c)Accuracy of the points in slice I and II in (a) by using
linear and quadratic functions; the error bar represents
the σ of the peak.

the source of electrons to calibrate the position of theanode. For each dimension of the delay-line anode, thesum of the times from the two ends, Tsum , should beconstant, see Fig. 1. We chose 3σ of Tsum as a gate to
cut the noise signal in both dimensions. The time information of each hole was obtained by projecting thepoints in the X axis and Y axis, and by ﬁtting it using
the Gauss function. It is not possible to use a linear
function to calibrate the relationship between the timeand position. Therefore, a quadratic function is chosen
since it has a higher accuracy as shown in Fig. 2(b)(c).
The position information of the holes after calibrationis shown in Fig. 2(a). For holes with a diameter of
1 mm, the resolution in both the x and y directions issmaller than 0.6 mm in σ, which is required for highresolution position sensitive detector.
An MCP with a delay-line anode that has a resolution smaller than 0.6 mm in σ is adequate for aposition sensitive detector. One detector has alreadybeen developed and is under testing.5) In the comingyears, other position sensitive detectors with the same
delay-line anode will be developed.
References
1) A. Ozawa et al., Prog. Theor. Exp. Phys. 2012, 03C009(2012).
2) D. Nagae et al., in this report.
3) Y. Yamaguchi et al., in this report.
4) S. Naimi et al., in this report.
5) Z. Ge et al., Accel. Prog. Rep. 50, 187 (2017).