Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 50 (2017)

Simulation and design of a large area position sensitive TOF MCP
detector at the Rare RI Ring
Z. Ge,∗1,∗2 S. Naimi,∗1 D. Nagae,∗1 Y. Abe,∗1 T. Uesaka,∗1 T. Yamaguchi,∗2 F. Suzaki,∗1 Y. Yamaguchi,∗1M. Wakasugi,∗1 S. Omika,∗1,∗2 N. Tadano,∗2 K. Wakayama,∗2 A. Ozawa,∗1,∗3 S. Suzuki,∗3 T. Moriguchi,∗1,∗3G. Lorusso,∗4 Y. Yano∗1 for the Rare RI Ring collaboration
In order to transport nuclei of interest individuallyto the central orbit of the Rare RI Ring1) (R3) withhigh eﬃciency and to improve the resolution of thein-ring TOF mass measurements at the R3, we plan
to develop a large area (∼42mm x 190mm) position
sensitive TOF MCP detector for R3, which has theproperties of low energy loss, good timing and highposition resolution.

Fig. 1. Structure of the MCP detector and description of
the parameters of the imaging mirror detector.

Information on the heavy ions that possess high energy can be reproduced by measuring the secondary
electrons (SEs) induced from conversion foils with
MCP which has a high intrinsic timing (20 ps-100 ps)
and position resolution (0.1 mm). Detectors with magnetic ﬁeld can’t be used inside R3 because of the accumulation of the bending power of the magnet forthe multi-turn circulation of fully stripped heavy ionsand the inﬂuence on the homogeneity of the magnetic
ﬁeld of R3. Therefore, we chose a mirror-electrostaticﬁeld-type detector for in-ring TOF position measurements. The detector consists of two chevron typemicro-channel plates (MCPs) coupled with a position
sensitive anode, a thin electron conversion foil, and amirror electric ﬁeld for bending the SEs ejected froma thin conversion foil (40 ug/cm2 ) passing through by
the highly charged heavy ion ( 78 Ni region with ∼ 170
MeV/nucleon energy for the next experiment).
2)
resolution, ananisochronous
isochronouscondition
condition
To achieve high resolution,
∗1
∗2
∗3
∗4

RIKEN Nishina Center
Department of Physics, Saitama University
Institute of Physics, University of Tsukuba
Department of Physics, University of Surrey

2)

is chosen,atatwhich
whichthethetotal
totaltime
timeofofﬂight
ﬂight consists
consistsis chosen,of 3 parts: the accelerating grid to the inner mirror
wires, bending path between the inner and outer mirror wires, free drift region from the inner mirror wires
to the MCP. The relation of the so-called isochronous2)
condition is D/(L1 + L2 ) = 0.236 UUmir. Uacc andacc
Umir are, respectively the acceleration potentials between the conversion foil and the accelerating grid, andthe mirror deﬂection potential between the mirrors aredescribed in Fig. 1 together with L1 and L2 .
To optimize the performance of the detector, a simulation was performed via SIMION.3) By keeping thehigh voltage (HV) potential of the MCP, accelerating
grid and inner mirror at -2500 V and by varying the accelerating HV of the foil and outer mirror grid at theisochronous condition we obtained the results shownin Fig. 1. With the increase of the accelerating HV,
the resolution of timing and position is improved andreaches a plateau at a certain HV value. The Y position resolution is better than that of X, which is dueto the mirror electric ﬁeld eﬀect in the Y direction.
From the simulation results, the intended timing andposition resolution of ∼100 ps in sigma and ∼1 mmin FWHM is satisﬁed, which is required for mass measurement (10−6 ) and velocity reconstruction (10−4 ).
The detector has already been constructed and is now
being tested.

(a)

(b)

(c)

Fig. 2. Simulation results by SIMION 3) (with a mean energy value of 2 eV and a Gaussian distribution in energyof the SEs). (a) Timing resolution (in sigma) as function of the accelerating HV potential (the HV diﬀerence
between the accelerating grid and conversion foil). (b)and (c) X- and Y-position resolution (in FWHM) dependence of the accelerating HV supply.

References
1) A. Ozawa et al., Prog. Theor. Exp. Phys. 2012, 03C009(2012).
2) N. Nankov et al., Wiss. Tech. Berichte FZR-423, 25(2005) (Annual Report 2004).
3) http://www.simion.com.

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