実験報告書様式（装置グループ利用）

Experimental Report

提出日 Date of Report
2016/9/15

実験装置名／ＢＬ番号 Name of Instrument/BL
4SEASONS/BL01
実験装置責任者 Name of the person responsible for the instrument:
Ryoichi Kajimoto所属 Affiliation: Materials and Life Science Division, J-PARC Center, Japan Atomic Energy Agency

１．研究成果概要 （a）装置グループ内の成果、（ｂ）ユーザー課題実装時における特筆すべきサポート、（ｃ）
ユーザー課題の執行状況について、まとめてください。A4 サイズ用紙使用のこと。
Outline of your activities.

Following results at your instrument should be reported in A4 size papers: (a)results of your instrument group, (b) significant user support works, and (c) statistical summary of userexperiments.
(a) Results of the instrument group
The experiments performed in the 2014 term are classified into the following three categories: (1)Performance tests to upgrade the instrument, (2) Calibrations of devices for stable operation of theinstrument, and (3) Preliminary measurements for new scientific themes or short supplementarymeasurements for users. For the category (1), we performed performance evaluation measurements of
new Fermi choppers, a radial collimator, N2 monitors, a new data acquisition mode using TrigNet, and a
IROHA2-based new instrument control system. For the category (2), we performed position calibrationof newly installed 3He detector tubes, phase calibration of choppers, and evaluation of backgroundscattering by a new IVC tail of the cryostat. As for the category (3), we performed test measurements ofphonon DOS of negative thermal expansion material ScF3 and magnetic excitation of pyrochlore
compound Ho2Ti2O7, in addition to a supplementary measurement for a user’s experiment of aniron-based superconductor FeSe. Here, we describe the results of the performance evaluation
measurements of new Fermi choppers in detail, which are the most outstanding outputs in theinstrument group use in the 2014 term.
Recently, we have developed two new Fermi choppers. One has a short (20 mm) slit package, and.
the other has a supermirror-coated slit package (we call the latter chopper Magic chopper). The short
chopper was designed to give higher transmission than the original chopper with a long (100 mm) slit
package, while the angular divergence defined by the slits should give same energy resolutions as
those for the original chopper. Figure 1(a) shows the flux gain of the new chopper, i.e., scattering
intensity of a vanadium sample divided by that for the original chopper, for several rotating frequenciesof the chopper. We found that the new chopper gives much higher neutron flux on the sample asexpected. The gain is particularly significant at low energies and at high rotating frequencies (forexamples, 1.9 for 43 meV and 250 Hz, and 17 for 18 meV and 300 Hz). Figure 1(b) compares theenergy resolutions (full-widths at half maximum of the elastic scattering profiles) obtained by the shortand original choppers. The both choppers give almost same resolutions as expected.

１．研究成果概要（つづき） Outline of experimental results (continued).

(a)(b)Fig. 1. Comparison of the performances of the short slit (new) chopper and the original long slit (old)chopper, evaluated by measurements of a vanadium sample. (a) Intensity gain. (b) Energy resolution
for elastic scattering
On the other hand, the Magic chopper is aimed to give high transmission especially for low energies
keeping the similar energy resolution as high energies taking advantage of the reflection by thesupermirror on each slit. Unfortunately, the reflectivity of supermirror in the Magic chopper installed inthis year was proved to be much lower than the ideal value due to a technical reason in themanufacturing process. Nevertheless, we performed the evaluation test of this “prototype” Magicchopper expecting we can characterize the basic performance of this kind of chopper. Figure 2 shows atime spectra of vanadium measured with the prototype Magic chopper compared with that measured
with the original chopper. Sharp peaks show elastic scatterings for different incident energies. While theMagic chopper gives lower intensity in a shorter-time (higher-energy) region due to the imperfection of
the supermirror, it gives substantial intensity in a longer-time (lower-energy) region where the intensity
for the original chopper disappears. We should note that the Magic chopper gives intensity even in thesecond time frame (dotted vertical lines). 4SEASONS has disk choppers to suppress the overlap of thesecond frame, though they were stopped in the measurements of Fig. 2. Although disk choppers are
not necessarily required on a conventional chopper spectrometer utilizing a Fermi chopper, the present
result proves the correctness of the adoption of the disk choppers on 4SEASONS. The obtained results
are quite useful for developing the Magic chopper in spite of the low intensity. Currently a new Magicchopper with much better supermirros is under development.

必要に応じて、A4 サイズの用紙に続きを記入して下さい。
Please use A4-size papers for further reporting, if necessary.

１．研究成果概要（つづき） Outline of experimental results (continued).

Fig. 2. Comparison of the time spectra of a vanadium sample measured with the Magic chopper (blue)
and the original chopper (red). The choppers were rotated at 150 Hz. Solid and dotted vertical lines
indicate time positions of the elastic peaks from the first frame and from the second frame, respectively.

(b) User support works
Instrument group staffs of 4SEASONS (R. Kajimoto (JAEA), M. Nakamura (JAEA), K. Ikeuchi(CROSS), K. Iida (CROSS), K. Kamazawa (CROSS)) performed user support works in pairs. One
technical staff from CROSS (M. Ishikado) provided technical support. In addition, many staffs
significantly contributed to the user support based on their specialty, such as software (Y. Inamura(JAEA)), sample environment (Y. Yamauchi (JAEA)), electric work (H. Tanaka (JAEA)), and machine
design (W. Kambara (JAEA), K. Aoyama (JAEA)).
(c) Statistical Summary of user experiments
25 General Use proposals, 2 Trial Use proposals, and 1 Element Strategy Initiative Use proposal wereapproved for BL01 in JFY2014. One reserved proposal in 2014A was given a beamtime. One General
Use proposal was canceled on request from the user. Unfortunately, 6 General Use proposals and apart of the Element Strategy Initiative Use proposal in 2014B were postponed due to the long shutdownof the facility caused by a fire accident in the muon facility and a trouble of the neutron source.

必要に応じて、A4 サイズの用紙に続きを記入して下さい。
Please use A4-size papers for further reporting, if necessary.