KEK-78-19 November 1978 A/1

KEK NEUTRON SOURCE AND NEUTRON SCATTERING RESEARCH FACILITY

Yoshikazu ISHIKAWA and Noboru WATANABE

NATIONAL LABORATORY FOR HIGH ENERGY PHYSICS OHO-MACHI, TSUKUBA-GUN IBARAKI, JAPAN KEK Reports are available from

Technical Information Office National Laboratory for High Energy Physics Oho-machi, Tsukuba-gun Ibaraki-ken, 300-32 JAPAN

Phone: 02986-4-1171 Telex: 3652-534 (Domestic) (0)3652-534 (International) Cable: KEKOHO SI. Introduction

This report describes a summary of the pulsed neutron source facility

KEK NEUTRON SOURCE AND NEUTRON SCATTERING RESEARCH FACILITY (KENS) which is under construction at National Laboratory for High Energy Physics (KEK), Tsukuba. The facility consists of a pulsed neutron source produced by spallation in massive target (either W or U)i irradiated by 500 MeV proton beam from the KEK booster synchrotron and a facility for neutron scattering exepriments. The KENS proejct was planned as an extension to by the neutron scattering researches with a pulsed neutron source (PNS) at Yoshikazu ISHIKAWA and Noboru WATANABE* Laboratory of Nuclear Science, Tohoku University and is considered as an Physics Department and *Laboratory of Nuclear Science, intermediate one to the final Japan Pulsed Neutron Source Project!' In Tohoku University, Sendai, 980 1974, a technical workshop was organized under the auspices of Grand In and Aid for Scientific Researches (G.A.S.R.) from the Ministry of Education, National Laboratory for High Energy Physics Oho-machi, Tsukuba-gun, Ibaraki-ken. 300-32, Japan where the possibility of constructing a pulsed neutron source by using surplus proton beams of a 500 MeV booster synchrotron at KEK was discussed. The results were published in a technical report?'' The proposal of the

Abstract KENS project was then presented to the KEK Advisory Council for Scientific

The outline of the KENS (KEK Neutron Source) facility is described. Policy and Management in May 1975, where the KENS was finally authorized The pulsed neutron source 1s produced by spallation in a massive element as a KEK facility. The budget for construction of the facility was approved irradiated by 500 MeV proton beam. The shleldings, cold neutron source, by the Government in February 1977. The facility will be accomplished guide tubes as well as various Instrumentations installed around the KENS until March 1980. are discussed briefly. The KENS facility is now organized as one section of the KEK Booster Synchrotron Utilization Facility which started from April 197B. This facility includes, besides KENS, two other experimental facilities, one is the meson physics research facility and the other is one to use high energy ** Presented at Second ICANS Wrokshop, Rutherford Lab., 10-15 proton and neutron beams for medical and biological purposes. The layout July (197B). of the whole facility is displayed in Fiq.l and the details will be reported separately?' Actual construction of the KENS facility is promoted by the construction workshop members organized also under the auspices of G.A.S.R..

-1- An Interim technical report describing the present status has been pub­ instrumentations expected to be installed in near future are Included. lished.' This paper is a summary of the report. A biological shield of the target, 4 m in height and B nTin diameter 1s placed near the center of an experimental hall. A target has two moderators; 12. Booster proton beam ' a polyethylene plate at ambient temperature and a cold moderator made by

The 500 MeV booster synchrotron which is going to be used for the a solid methane plate at 20 K. Nine beam tubes glancing at the normal KENS serves as an injector to a 12 GeV proton synchrotron. ,.ie machine moderator deliver the epithermal and thermal neutrons to both'sides of

1 was designed to operate at 20 Hz with the maximum beam current of the shield, while the cold neutron beams from the cold neutron source 12 are transported to another experimental hall (cold neutron area) through 0,6 x 10"- ppp and the designed value has already been obtained. In a three neturon guide tubes. There is one beam tube (C4); 1n thefmain hall normal operation mode, the first nine pulses 1n every two seconds are which looks directly at the cold neutron source with a large glancing injected to the main accelerator and remaining thirty-one pulses are angle. The data acquisition as well as machine control systems! will be delivered through a 110 m long beam transport section to the Booster installed In a separate room. Since the medical group Is going to set up Synchrotron Utilization Facility where the beams are shared by three a facility for the high energy neutron irradiation and therapy just 1n groups. The characteristics of the booster beams are summarized in front of the target, the target station is designed to move back to an Table 1. The beam size at the neutron source target 1s expected to be open space (target handling area) where the target or moderators are 24 (horizontal) x 13 (vertical) mm . demounted. Table 1. Characteristics of Booster Proton Beams

14. Target stations Energy 500 MeV The KENS target assembly consists of a target, two kinds of moderator, Repetition rate 20 Hz Beam pulse width 50 nsec Be reflector and their shiledings. We start with a tungsten target, but 12 Space charge limit 2.6 x 10 protons/pulse this will be replaced by depleted uranium-23B as soon as we get familiar With the handling of the spallation neutron source. The tungsten target Max beam Intensity achieved 6.0 x 10 protons/pulse u consists of two blocks of tungsten, each having a dimension of 7B x Beam emlttance observed horizontal: 44 nrn-mrad H L at 4.4 x lo ppp vertical : 20 mm-mrad 57 x 60 mm. Total length of the target is therefore 120 ran, which is sufficient enough to stop 500 MeV protons to produce the spallation 53. KENS facility neutrons '. The maximum heat production 1s estimated to be 0.63 kw for Figures 2 and 3 are the layout of the KENS facility where the whole tungsten and 2.5 kW for uran1um-238 and the target 1s cooled by circulation of pure water. The maximum gap of water cooling channels is 2 urn to

•2- -3- minimize the neutron thermalization in the target and a special care 1s system has a very low efficiency. The addition of the graphite reflector taken to prevent from production of air void. The: water is circulated to it, however, increases the efficiency by about three times.as shown with a pressure of 3 kg/cm with the maximum flow rate of about 20 fc/mln - by (d) or (e). The comparison of the configurations (d) andj(e) suggests condition to depress the voids. Two moderators are placed upper and below that the configuration (d) where the neutron beams are extracted from the target as schematically shown in Fig.4 and they are surrounded by Be both sides of the moderator is more economical than (e). Therdecrease reflector with an approximate diameter of 600 ran and 585 mm 1n height in neutron beam intensity of the case (d) relative to the case (e) 1s (total weight is about 200 kg). only 14 %, while the number of the beam tubes can be doubledifor the case (d) compared with the case (e). Therefore we decided to adopt the con­ The ambient temperature moderator and cold moderator are decoupled figuration (d) for the KENS. The conversion efficiency of J^.= 2.73 x respectively by B.C and Cd from the reflector so as to decrease the 10 ntl/str'nf was "len 0Dtai|,ed f°r a designed valueof d = 3.75 cm. beam pulse widths. The whole target system 1s set on a target station

Note that the reported value of Jtu = 8.1 * 10 ni^/str.n^ measured by which can be moved backward on a railway together with a refrigerator Boland et al. for a similar system (Musta graphite reflector decoupled for the cold moderator as displayed In F1g.4. by Cd with d = 7.5 cm) ' is only about 1/2 of the value on anextension

The target-moderator-reflector configuration adopted for the KENS of the line (e). Since it is anticipated that the gain factor increase was determined based on the resutls of a mock-up experiment performed 1n -3

August 1977. The neutron target was simulated by a cylindrical Am-Be by a factor 1.5 by using the Be reflector, the value of Jtu = 4.1 * 10

neutron source of 1 CI and the Intensity of total thermal neutron flux nt|7str.nf can be adopted for evaluation of the neutron intensity of the ru. from the surface of a polyethylene moderator at ambient temperature KENS. was measured as a function of the distance d between the centers of the S5. Neutron beam Intensity source and the moderator. The effect of the Be reflector was simulated The 4ir equivalent peak flux at the surface of the moderators In by a graphite reflector with a small amount of BeO blocks (about 6 liters the KENS was estimated using a following equation In total) only at the central part. The conversion efficiency of the moderator - reflector system defined by nt_/str. nf, where n. Is the „ _ 4*S„J(E) neutron source Intensity, 1s plotted against d in Fig.5 for various types *4TT (E) " A.f.S(E) • of configuration as displayed In the figure. The configuration (b)-250 or (c) has a good efficiency, but It has a disadvantage that the spallation where S : number of neutrons produced 1n the target per unit time neutrons come out through the experimental beam tubes and Increase the back N (1.8 x 1014 n/sec), ground. The configuration (a) 1s good for the S/N ratio, but a bare A: moderator surface area viewed from the beam tube (100 cm ),

-4- -5- where J(E): number of neutrons emitted from the moderator surface toward 0 (E): pulse broadening in the moderator at an energy E for the the beam tube per unit solid angle, per unit energy around E, & function source pulse per source neutron, 0 (Ed): pulse broadening in the reflector at a moderator-reflector f: repetition rate (15 pps), decoupling energy Ed for the 6 function source pulse, 0(E): pulse width (FHHH) of slow neutrons at energy E.

0 (Ed) is assumed to be given 1n case of the Be reflected system, by d(E) is estimated from the measured spectrum J°(E) (1n an arbitrary unit) p

9 for a bare system ' and Jth experimentally determined by the mock-up 0r(Ed) = 8/VEd(eV) (usee) (6) experiment ' using a following relation The values of 0(E) calculated using the measured values :of 0(E) are plotted also in F1g,6 against energy E for both of Cd decoupled !(Ed = 0(E) - -x & J°(E), (Z) c J" (E) dE 0.4 eV) and B.C decoupled (Ed - 500 eV) systems. The 4it equivalent Jo peak flux *4_(E) estimated by using J°'(E) and 0(E) 1n the figure 1s plotted The value of J(E) at E=l eV is also given by in F1g.7.

The peak flux from the KENS cold neutron source was estimated using

the measured spectrum J°(E) ' and the measured half width 0m(E) for J0 J(E) dE solid methane at 20 K. ' An assumption was made for the evaluation of

3 J°(E) for a 10 x 10 x 5 cm polyethylene moderator at ambient temperature J(E) that J(E) at 1 eV for the solid methane moderator is the same as is shown 1n Fig.6. They are normalized by a value at 1 eV. The value of that for the polyethylene moderator at ambient temperature. For J.. , J(E) at 1 eV for the reflected system 1s then obtalend by using Eq.(3) as a value of 2.5 * 10 nt|Vnf str. was adopted from Fig.5 and d = 4.8 cm. The 4ir-equ1va1ent peak flux 'of the cold neutron source Is also plotted

EJ(E)|n eV» Jth/4.6 , W In F1g.7. Note that at the themal neutron region the peak flux of the KENS 1s not so much different from that of the medium size reactor, but

3 with Jt|) = 4.1 x 10' nth/nf str. for the KENS (Cd decoupled system). in the eplthermal region the peak flux 1s higher than that of the ILL

For the B4C decoupled system, Jt() was assumed to decrease by a factor 1.5. hot source. In the cold neutron region! though the flux is several By neglecting the source pulse width, 0(E) can be expressed as times lower than that of the ILL cold source, it is still higher than that of the high flux reactor without the cold source. Therefore we

3(E) » [e£(E) + 0*(Ed)]1/Z , (5) think that the KENS 1s a useful neutron source in the neutron energy

-7- regions outside of the thermal neutron region. If compared with the PNS deslgn was reported separately! ' The bird's-eye view of the!KENS shield­ of Tohoku Univ., the KENS has the peak Intensity 100 times higher than ing 1s displayed in F1g.9. the former and therefore it would be appropriate for a next step neutron source. 87. Cold neutron source

The cold neutron moderator Installed at KENS will be made by a 96. KENS shielding W 0 H 3 ' ! solid methane plate of 13 x 5 x 15 cm which is placed In the upper The biological shield for the KENS was designed so as to satisfy side of the target (Fig.4). The cold neutrons are extracted In a direction the following conditions of about 45 degrees from the proton beam direction. The distance between 1) The researcheres can get access to their own spectrometers even the surface of the target and the bottom of the moderator is 19.5 mm. in the operating time. The radiation level at the surface of the The moderator 1s cooled down to 20 K by circulation of helium gas which biological shield should be less than 0.8 m rem/hr. Is cooled by a small cryogenerator with a cooling power of 25 U at 20 K 2) The total dose equivalent at the boundary of KEK territory should be (PGH 105). The moderator and a heat exchanger are encased in a small small enough to be disregarded compared with the natural radiation vacuum vessel 2B0 rnn 1n height and 190 mm 1n diameter which: is1 set inside level. the Be reflector. 3) The maximum distance from the target to the surface of the shield Several mock-up tests had been performed before the optimal moderator in the horizontal direction should be less than 4 m. The height size as well as the cooling system were determined. It has been reported of the shield should not exceed 4 m because of the necessity of that solid methane Is the best material for getting pulsed coldneutronsl ' reserving the working distance of a 10 ton crane In the main hall. Figure 10 is the results of a mock-up experimenet performed at>the cold 4) Total budget for the shield is limited. neutron facility of Hokkaido University using an electron Unac to decide Figures 8 a and b show the cross-sectional views of the biological shield. 13l The target is surrounded by Iron blocks of 1.25 m thick which are covered the optimal moderator size. ' A solid mesltylene moderator which has by heavy concrete wall. Each of ten beam tubes 1n the main experimental similar characteristics as solid methane at 20 K was placed 5 cm above hall 1s equipped with a 0.9 m long Iron shutter which moves In the vertical Pb target and the neutron flux intensity distribution of the moderator direction. Iron and concrete shield blocks on the top of the target as Was measured as a function of the vertical distance h. The results of well as over the target handling area can be removed by the 10 ton crane three different moderator sizes are displayed in the figure. The results so as that the target assembly with high radioactivity can be handled suggest that the neutron peak Intensity becomes insensitive to the height from the top of the shield using the crane. The details of the shield h and the width of the moderator when their dimensions exceed 10 cm. Therefore a size of 12L x 5 x 15" cm Is appropriate to the moderator size. The figure also shows that the flux intensity becomes maximum -B- -9- around h = 4 cm for all cold neutron energies. Therefore the neutron 58. Cold neutron guide tubes guide tubes are designed to look at this position. Three neutron guide tubes are planned to be installed at the exit

Another mock-up experiment has established a method to get a dense channels CI i C3 and they transport cold neutrons to the cold neutron solid methane plate; the moderator case at 90 K (the melting point of experimental area. Each guide tube consists of three parts; a 3.5 m CH^) should have little temperature gradient (AT < 1 K) with lower long straight section inside the biological shield, a curved section with n ' II I temperature in the bottom. It 1s also Important to cool slowly through a cross section of 20 x 50 ran and a radius of curvature of 820 m, which i the melting point. is 9 m long and is placed Inside the light shield area (marked as a !' I water pool in Figs.2 and 3, but actually the water 1s not used) and a A mock-up experiment to know the radiation heating by spallation straight or a curved tube to the spectrometer. N1 coated float glass neutrons was also carried out using 500 MeV protons (4 Hz, 4.8 x 10 pps) is used as the reflector. 1 at the beam dump room (cf F1g.l). A mesltylene moderator plate 10 x In order.to know the transmission characteristics of, the guide, a 10 x 5 cm in dimensions was placed 1,5 cm above a tungsten target. The computer program for simulation calculations was constructed, 'jWhich moderator was cooled down to 12 K by circulation of liquid helium with enabled us to know the spaclal and energy distributions of neutrons at a cooling power of about 12 W (at 15 K). A cryostat used in the experiment a desired cross section of the guide. We also examined the transmission has the same dimensions as that would be adopted for the KENS. The K V 2 efficiency of the polygonally approximated guide. proton beam size in the beam dump was measured to be 6 x 3.5 cm.

The result of one hour's running Indicated that the moderator tem­ The usefulness of the guide tube are well recognized!1n case'of the perature rlsed up to 13.5 K from 12 K, while the temperature Increase steady reactor. However the KENS facility will provide the first' example of the outer surface of the aluminum moderator case was less than 1 K, of the guide tube combined with the pulsed neutron source;. Besides a

1 suggesting that the heating was mainly due to the neutrons entering into merit of transporting the cold neutrons to the clean area ; the-guide the cold moderator. The y-ray heating was found to be negligible as was tube now has an advantage to make up the demerit of the long pulse width expected. The quantitative evaluation of tfie neutron heating power is of cold neutrons (100-200 psec) by Increasing the flight path. Low

; now in progress, but we need to anticipate a temperature rise of order repetition rate of 20 Hz enable us to obtain a quasi-cbntinUous 'neutrons o o of 10 K for the cold moderator of the KENS if the cooling power is the with wave lengths ranging between 4 A and 12 A at the 'end^of 25;mlguide same as the mock up experiment. The details of the mock-up experiments tube. Such a beam can be used effectively in various purposes as described will be reported successively. in the next section.

-10. -11- 59. Instrumentations absorbing nuclei for thermal neutrons) can be carried out. (exist) Since the KENS 1s a medium flux neutron source, the facility should 1.3 Neutron diffractometer under high pressures (50 kb *" 100 kb) (H5) be used complementary to the steady reactor; the research fields should (planned) I > be restricted to those which take advantage of the characteristics of 1.4 Neutron diffractometer at very low temperatures (below 0.1 KV and/or the spallation pulsed neutron source. Based on this idea we selected at1 high magnetic fields (>300 kOe) i ' . following four research fields on which we put an emphasis 1n the KENS (planned) ' 1 facility. They are; 1.5 High resolution powder neutron diffractometer (C-4, backward)! 1) EpUhermal neutron scattering, particularly with polarized neutrons. This is a powder dlffractometer with a long'flight path of more 2) Cold neutron scattering, particularly with white polarized neutrons. than 20 m. In cooperation with the profile analysis method, [ an 3) Neutron scattering under the extr^ .i condltons and 1n;non equilibrium accurate structure determination can be performed (AQ/Q < 10 |) states. (planned) ' 4) Neutron scattering by controlling the resolutions.- 1.6 Small angle scattering Instrument (C-1) In order to practice the researches 1n these fields, fifteen spectrometers Combined with either one dimensional or two dimensional position are proposed to construct, the layout of which Is shown 1n Figs.2 and 3 sensitive detector, spadal distributions of long disturbance and their characteristics are briefly described below. 3 ' ' ' with 10 < Q < 1 A will be studied, (construction determined)

'•'•{• ' ' 1.7 Polarized cold neutron scattering instrument (C-3) ,

•':•'•'<• ' • , , l 1. Elastic scattering Instruments White cold neutrons will be polarized by: means of total reflection 1.1 Four circles single crystal dlffractometer (H6) from Fe-Co magnetic mirror collimators made by plastic thin films. i i This dlffractometer, equipped with linear position sensitive detectors The direction of polarization can be reversed in every two seconds enables to scan at the same time a wide range of theiredprocal space. by changing the direction of polarity of the magnetization of the A technical development of using the position sensitive detector to mirrors and the magnetic parts of the reflected neutrons can be the TOF diffractometer is now 1n progress at PNS of Tohoku Univ.. separated from the nuclear parts in every two seconds. The polarization The diffraction in non equilibrium states as determination of the analysis will also be performed by the same method. The techniques atomic structures 1n a process of the crystal growth can be done, are now under development. A preliminary experiment Was carried (construction required) out with the PNS of Tohoku Univ. and the feasibility has been 1.2 Eplthermal neutron diffractometer15' (H2) confirmed. ' A prototype spectrometer will be constructed in-$h1s By using epithermal neutrons with energies higher than 0.5 eV, year at this Laboratory, (construction determined) neutron diffraction from materials with Cdj Gd or Sm (highly

-12' -13- Total scattering spectrometer proton; polarized target group at KEK using a ethylene glycol

:l 1 High counting rate total scatteringispectrometer (H4) polarized proton filter indicates that this method 1s promising119! '1 This spectrometer is designed to increase the counting! rate as The;technique 1s now under development by collaboration of polarized much as possible .at the sacrifice of the angular resolution (AQ/Q > proton target group at KEK and neutron scattering group. 0.02). The machine will be used tojstiidy the:structure analysis 1n (construction required) < non-equH1br1 urn states, (construction/determined) 3.4 Low angular resolution cold neutron spectrometers (C-W; forward) 2 High momentum transfers total scattering spectrometer'(H5) By time focussing of the monochromatlzed neutrons from large mono- The machine is designed so as to be able to detect the high momentum chromator crystals, neutron flux at the sample position will be in­ transfers up to 100 A and this will be used complementary to the creased at the sacrifice of the angular resolution. The machine previous one. (planned) will be used to practice small energy transfer incoherent scattering (0.5 meV < AE < 20 meV) as the study of the adsorped materials.' A Inelastic scattering spectrometers prototype of this machine was installed at PNS of Tohoku University? ' 1 Multi-crystal analyzer spectrometer (MARX) (H-l) (construction determined) ' i This Is a typical MARX type spectrometer which enables us to detect 3.5 High energy resolution spectrometer (C-2) , ! .'tai' •' '•• ;-''•;-!• the scattering 1n the constant q mode! ' The spectrometer 1s designed ' •• • • I i The spectrometer will be Installed at the end of the 25 m guide tube. to cover the energy transfers between 50-meVi and:200:meV and will •:•:•• i' i I The effective Intensity of scattered neutrons is planned to be Increased be used to extend the researches done with"the mediumjflux steady by adopting the time correlation method to the quasi-continuous neutron reactor, (construction determined) beams, the technique of which is now under development (planned) 2 Chopper monochrometer spectrometer (H5) 3.6 Resonance detector spectrometer (H-7 backward) ' This spectrometer equipped with a Fermi type chopper monochrometer 23B: \ is the most universal spectrometer which covers energy transfers U has a very sharp resonance absorption at an energy of 6.67 eV. between 50 and 500 meV and 1s particularly effective for Incoherent The y-rays emitted after neutron capture are detected by a -y-ray inelastic scattering. However, the technique xo synchronize the scintillator which was served as an energy analyzer. The spectrometer chopper rotation to the neutron pulses should lie developed, which can be used to measure the energy transfers of order of 1 eV. The 1s now under consideration, (planned) KENS 1s quite promising 1n this field because of the very short 3 Polarized epithermal neutron spectrometer neutron pulse. A preliminary measurement using a Ta foil was suc­ Polarization of epithermal neutrons will be achieved by using a cessfully performed at PNS, Tohoku Univ. and the feasibility was polarized proton filter, A preliminary experiment performed by 211 confirmed. ' (planned)

-14- -15- ' ; • • i ' i 10. Data acquisition system for the KENS facility one mode,while another will be used exclusively for the list mode. The j

The KENS data acquisition system handles the time |of flight neutron list mode data;are edited at once and will be displayed on a graphic l scattering data from the KENS spectrometers.: Tjie system includes the display. , ^magnetic tape, a paper tape puncher and a line printer are following functions; i) data collection, ii) data control and transfer, available to,keep:the output 1n a proper way- One Interface equipped 111) data handling and display and iv) data output. ; with 16 inputsi (detectors) having the functions oftime analyzer* monitor­

ing data distribution is designed to cover two sepctrometers.-;:The CAHAC From the view point of data collection* the spectrometers are classified I

Into two categories according as more than 16 counters 'jar position sensitive system might be:adopted. Each spectrometer has one data control panel

.,.!!'•':' ' i detectors are used in a spectrometer or riot, , Since each single counter with a simple data display as well as order keys. The mechanical control needs about 1024 total channel numbers, even one spectrometer 1n the of the spectrometer as well as the control of the sample atmosphere will i former category requires large storage in central process unit (C.P.U.). be made separately using a mini- or micro-computer. In this case we plan to adopt the list mode system as data collection, The data acquisition system described - a central control system - where both time of flight and position of the event are stored in memory • I ' " 1 is mainly theisame as that we are adopting at PNS, Tohoku Univ-, !"lt;;has at each event. When the storage in C.P.U. 1s full of data, these are several disadvantages as interference between different spectrometers or converted to a spectrum and 1s transferred to a magnetic disc. In the that one trouble, in a computer affects seriously many spectrometers. latter case, the TQF spectrum of each detector is directly stored 1n memory by the add one mode. When the number of neutrons coming to one However this sytern is inevitable for the KENS facility where the^large channel exceeds 2n/2 usee, which would be the case for the high counting amount of data should be handled. We are now constructing a software rate spectrometer, the counting rate becomes higher:than the cycle time system to minimize the Interference or the disturbance based on our of the computer memory (generally about 1 usee) and we can not store experience at PNS, the data by direct memory access. In order to overcomethe difficulty, There is also a possibility to transfer on-line the data to,a-KEK we plan to attach a small size scaler (for example, of 6 bits (64 counts)) large computer (HITAC B800/BB0Q Multi-system) through a data free way. to each channel and the data will be transferred to the memory for every which has been constructed to connect the computer center and the experi­ 64 counts. mental hall for the high energy physics and which still has a space to transfer other data. The merit of using this system 1s now under '• A complete data acquisition system which we plan to have 1s displayed consideration. 1n F1g.ll. There are two C.P.U,, each having a core memory of 128 k words and a magnetic disc (32 M Bites). The disc should be accessed Gil. Future aspects of KENS project independently from either C.P.U,. One C.P.U. is mainly for the add The present neutron flux of the KENS is not sufficient enough to

•16- -17- 6) R.R. Fullwood, J.D. Craner, R.A. Haarman, R.P. Forrest, jjr. and practice ambitious experiments and the projects to increase the intensity R.G. Shrandt: Neutron Production by Medium Energy Proton on is now under consideration. One project is to change the injector system Heavy Metal Target LA-4789 (1978) r I ' to inject H" ions and to increase the proton, current up to the space charge limit of the booster (2.6 x 10 ppp). This;modification makes 7) N. Watanabe, M. Misawa and S. Yamaguchi, to be published (see also increase the neutron intensity four times higher, than the present one. (4) P-42) | '

The KENS biological shield is designed to allow this!Increase. We consider 8) B.C. Boland, G.C. Stirling and A.D. Taylor: Reflector Studies for •I ,. this project as the phase II of our project. The next state is to con­ Pulsed Neutron Moderators, RL-77-140/A Dec. (1977) I i struct a new intense proton accelerator with the intensity of the same 9) J.M. Carpenter and G.J. Manner: Evaluation of the ZGS-Booster as order of magnitude as SNS or IPNS II and the neutron;flux of order of an Intense Neutron Generator, ANL-5SS-72-T(1972) ' ' 10 n/s cm will then be obtained. The construction of this accelerator 10) K. Inoue, N. OtomD, H. Iwasa, and V. Kiyanagi: J. Nucl. Sc1. Tech. is now discussed in the neutron diffraction group inJapan. 11 (1974) 228 11) K. Inoue, Y. Kiyanagi and H. Konno, to be,piiblIshed Acknowledgement 12) N. watanebe, K. Katoh and R.H. Thomas,: Shield Design for KENS, This report is a sumnary of the KENS project promoted by members KEK Report 78-7, Note No.6 (1978) Df KENS group to all of whom the authors acknowledge;sincerely. 13) K. Inoue, Y. Kiyanagi, H. Uasa, Y. Ishlkawa and N. -Watanabe, to be published (See also (4) p.84) References 14) S. Ikeda and Y. Ishlkawa, to be publlsned 15) Y. lshikawa, N. Watanabe, H. Sekine,. K. Tajima and'K. Takei, 1) Technical report of the workshop (G.A.S.R.) on "Repetitive pulsed Proc. Neutron Diffraction Conf,, Petten, Aug. (,1975) 360 neutron source project in Japan". March (1971) 16) C.G. Windsor and R.N. Sinclair; Act. Cryst. A32 (197.6)|95 Z) Technical report of the workshop (G.A.S.R.) on the KENS project, 17) Y. Honma: Master thesis march (1977) (see also:;(4) ;P/13i) March (1975) 18) C.G. Windsor, R.K. Heeman, B.C. Boland and D.F.R. Mildner, 3) H. Sasaki: A report presented at 2nd ICANS workshop, Rutherford Harwel1 Report Lab., 10-15 July (1978) 19) S. Hiramatsu et al., JAERI - memo 7469 (1977) i 4) Technical report of the workshop (G.A.S.R.) on Construction of 20) N. Watanabe, Y. Ishlkawa and K. Tsuzuki, Nuclear Instru. Methods KENS Facility, July (1978) 120 (1974) 293 5) V. Arakita et al.: IEEE Transactions on Nuclear Science, Vol.NS-24 Zl) N. Watanabe and D.L. Price, to be published (See also. (4) p.132) No.3 (1977), 1977 Particle Accelerator Conference. Accelerator

Engineering and Technology, Chicago, March (1977)

-19- -18- POKER SUPPLY & LOCAL CONTROL ROOM

FOB BEAM DUMP LINE

TO O I MEDICAL TREATMENT ROOM MITH NEUTRON

DATA PROCESSING t CONTROL ROOM

FOR NEUTRON PHYSICS HI: Multi Angle Reflecting Crystal.Analyzer Spectromete H2: Epithermal Neutron Diffractometer 115: Hi-Q Total Scattering Spectrometer. H4: Rapid Counting Total Scattering Spectrometer HS: High Pressure Diffractometer C4-1: Crystal Monochrometer Neutron Spectrometer H6: Single Crystal Diffractometer C4-2: High Resolution Powder Neutron Di'ffractometer H7: Resonance Filter SpectrometerCbackward) H8: High Energy Transfer Neutron Spectrometer with Neutron Polarizer Chopper Monochrbmetcr Neutron Spectrometer

Fig.2 Layout of KENS facility: Main experimental hall CI: Small Angle Diffractometer C2; Correlation Type Cold Neutron Spectrometer C3: Cold Polarized Neutron Spectrometer

KENS Neutron Scattering Facility

Fig.3 Layout of KENS facility: Cold neutron area Cold Neutron Experimental Area Cold Neutron (to Experimental Area II) Neutron Source ^jEpithermal Neutronfto Experimental Area KB)) He Gas Refrigerator -^SSil.punr

Thermal Neutron (to Experimental Area 1(A))

Target Cooling System

Neutron Souce Support Fig.4 Bird's-eye view of KENS target station (b;-2bO

20 30 40 d (mm)

Fig.5 Thermal neutron conversion efficiency nth/str. nf of moderator reflector systems with various configurations plotted against distance d between centers of neutron source and moderator.

-24- r10^ -, , ,—,—r-i i i | -•• T'—r n *JLL(Cold) I ' "• I

KENS Solid Methanet20K) ,- -JLL -10' J°(E) Solid Methane (20 K) Polyethylene .

(300 Kl (Msec) KENS .,.,' Cd decoupled v ^Pdyethylehe (300K) > :ltf' /" DIDO Qj / / ILL(Hot) . / / :10"

decoupled TOHOKU Linac ..• -L LJ-LL I" I ll »-3 2 1 u 3 2 1 10" io- 10: 10 10" 10" 10" 10° E(eV) E(eV) Fig.6 Neutron spectrum J°(E) from bare moderator and neutron a F1g.7 4ir equivalent peak neutron flux of KENS estimated using data pulse width 0(E) used for evaluation of neutron spectrum of 1n Fig.6. Neutron flux intensity spectra of other sources KENS. are also plotted for comparison. -25- -26- (a)

Ordinary Concrete

(b)

^ ^Ws WMY/A Heavy Concrete

0 1 2m

Fig.8 Cross sectional views of KENS biological shields (a) perpendicular

to proton beam, (b) along proton beam.

Neutron Source and Biological Shield Movable Shield

Fixed Shield Neutron Beam Shutter

Cold Moderator Refrigerator Gas Reservoir Reflector

Neutron Beam Hole-VH

Neutron Beam Tube

Target Station

Fig.9 Bird's-eye view of KENS biological shield -6Z-

Neutron intensity

» \ \ \ N 1 \ \ S N 1 \ \ \ \ • ••••• •• 1 \ ' * \ .. ~ a, ~ !l Je is if ,'f Ol I / # / / D" ill//

III// S -fJT III / / ' s 3 III// s ,' III ' • S s • •••*. ••--*- 1 / / / / • y _l ' / ' / / ' O CJI ill//' ," / // ' ' / m • • »•»-•• -» n III,' " / // /.' ' s 3 XI I Ml/'/,' W'III/// /

,; .«y;;s--,.

i i i '

i i

i / / ID iii /* / lit / o in * 7 r 7 / X ~~,-? >

-T"

l 5 "^ IN» li inni !3 / 3 jS 2 3 3*-4.- X 'I << ii _i—k" 3 !.'///'-' 5 (1) |»»»» • • • o -v 3 ^ O Multi Angle Reflecting Crystal Analyzer Spectrometer Epitermal Neutron Diffractcmeter Hi-Q Total Scattering Spectrometer Rapid Counting Total Scattering Spectrometer High Pressure Diff ractometeir Single Crystal Diffractometer Resonance Filter Spectrometer (backward) High Energy Transfer Neutron Spectrometer with Neutron Polarizer Chopper Monochrometer Neutron Spectrometer Small Angle Diffractometer Correlation Type cold Neutron Spectrometer Cold Polarized Neutron Spectrometer.

Fig.11 Layout of KENS data acquisition system