Matsuki, Seishi

Miyatake, Yoko

Yamashita, Sukeaki

Kyoto University Research Information Repository

TitleMeasuring Projector for the Analyses of Bubble-ChamberFilms (Memorial Issue Dedicated to the Late ProfessorYoshiaki Uemura)Author(s)Yamashita, Sukeaki; Matsuki, Seishi; Miyatake, YokoCitationBulletin of the Institute for Chemical Research, KyotoUniversity (1974), 52(1): 58-62Issue Date1974-07-25URL http://hdl.handle.net/2433/76540RightType Departmental Bulletin PaperTextversionpublisherKyoto University       Bull. Inst. Chem. Res., Kyoto Univ., Vol. 52, No.  1                Measuring Projector for the Analyses of                       Bubble-Chamber Films                Sukeaki YAMASHITA, Seishi MATSUKI,and Yoko MIYATAKE*                                       Received January 5, 1974            Three measuring projectors were contructed for the analysis of the bubble-chamber films. The          measurement accuracy was obtained about 10 pm in the scale of filmplane.                                I. INTRODUCTION          The analysis of bubble-chamber films is one of the most important tools for study-     ing the particle interaction. Three measuring projectors of image plane digitizer type      were constructed with the aim of the analysis of bubble-chamberfilms.         The image plane digitizer consists of the film projector and the measuring machine.      The projector is also used for scanning the films. The imageof the reaction tracks      is projected on the measuring table and the coordinates of several points along the track       are measured with a co-ordinate digitizer. The digitized co-ordinate values are punched       out to computer cards. Three view images are used to reconstruct he three-dimensional      track in the bubble chamber.         The data analysis of the bubble chamber films consists of the  following:      (1) Scanning; searching for and recording all interesting events in the projected          images of the films.      (2) Measuring;determination of the co-ordinates of several points along the track          contained in the corresponding event in the three views.      (3) Geometrical reconstruction of tracks; fitting a track to a helix through the measured           points in space.      (4) Fitting to the hypothesis; making a hypothesis about the nature (namely, mass)           of particles involved, and determination of momenta usingmagnetic field value,           and constraints of the conservation of four momentum make possible to calculate          a chi square for the hypothesis in question, and choice of the most probable reac-         tion hypothesis by repeating this procedure for every otherhypotheses.      (5) Physical analysis.          The constructed measuring projectors are profitable in practice for measuring the      events appearing in the bubble-chamber films. In this paper, some performances of      the projectors are reported in brief.                                 II. PROJECTOR          A projector can set the three rolls of films, each of which corresponds to the separate         * 1~1~(~f~~~C 'Aa- : Department of Physics, Faculty of Science, Nara Women's            University. ( 58 )                                  Measuring Projector stereo-view. A set of three-view images can be compared to each other on the  measur-ing table by switching the projector lamp. Film driving is performed by a pinch roller which nips the periphery of the film. The driving speed is controlled by a lever con-nected to a variable resistance.    Each film roll of three views is drived separately, or, if required, all together. The luminosity of the image can be controlled to be the most feasible for measurement. The magnification of the projector is about ten. To ensure the constant magnification and the fixed film position, the film is attached to a glass plate by means of vacuum pumping. When the film is drived, the vacuum turns off by a magnetic valve.    A 500 ft film roll is turned back with a rather high speed, after the end of scanning or measuring procedure. This turn-back drive is performed roll by roll or all together.                        III. MEASURING DEVICE    The measuring table has two magnetic scales which are set orthogonally to each other. The magnetic scale has a resolution of 50 µm. Two magnetic pick-up heads are drived on the surface of an aligned magnetic dipoles, and are set so that the out-put signals of moving have phases different from each other by ir/2. The preamplifier has two out-puts, one of which corresponds to the forward moving and the other the reverse moving. At the forward out-put, one pulse appears for every forward moving step of 50 pm, and at the reverse out-put, one pulse appears for every reverse moving step of 50 rim. After pulse shaping and passing through a mutual inhibit circuit, an up-down counter is drived by the forward or the reverse pulses.    Track measurement is done by fitting a small light spot (about 0.02 mm in diameter) on a track. The light spot can be moved on the measuring table in the range of 150 cm (X-direction) and of 60 cm (Y-direction). The X—Y co-ordinates are determined by the counts of pulses from the magnetic-scale heads.    The informations about each event, i.e., the frame number of the film, the bubble density of the track, the operator number, the date, etc., are set and fed to a card punch-er. Then the measurement proceeds as follows : (1) Measurements of fiducial marks (reference points in the bubble chamber). (2) Measurements of six points along each track belonging to the interesting event.    For example, measurement is done for five tracks containing the incident track     for a four-prong event.    When a measuring button is pushed after fitting the light spot to the interesting point (a fiducial mark or a point on the track), the numbers of counts corresponding to the X—Y co-ordinates are registered in shift registers (five decades for each co-ordinates), and they are sent successively to a puncher driver by shift pulses with the interval of 0.1 sec.             IV. CORRECTION OF THE OPTICAL DISTORTION    The projected image is usually distorted by the projector lens aberration. Calibrat-ed mesh points of 6 x 16 on a film were used to correct the image distortion. The projected mesh points were measured ten-times and the measured values apart from ( 59 )                                           S. YAMASHITA, S. MATSUKI, and Y. MIYATAKE            the averaged value by three-fold of the standard deviation were rejected and the average            was again taken from the remainders of measured values. In order to obtain the            coefficients of the transformation equations of third order by the least square method,            mesh points of 80 were used excepting the extreme 16 points, because the use of 80            points was more favorable than involving the 16 points which caused large errors in            the coefficients due to the large optical distortion. The extreme portion of the image            plane is not used in the actual measurement, and the transformation using the third            order equations was sufficient to correct the optical distortion within the measurement            error of the point. An example of the optical distortion is given in Fig. 1, for the             MP-3  View-1 projection.                       DISTORTION MAP 6 r ' r- — - • - • r 1 -I a .2 a           L ts. L L_. L 1_ L L L I1 1 1 ,1L L L L L L L L Lf. t f I I f 1 1 [ LLLLLLLLLLLLL., 1mm                     Fig. 1. Optical distortion of the projector (MP3, View-1). Arrows show the direction                             and the magnitude of the second and third order corrections.                                 V. ERROR OF MEASUREMENT               Now, we are carrying out the analysis of the four-prong events caused by 7 GeV/c            anti-protons. Helix fits of tracks are done by the reconstruction program (THRESH,           developed at CERN). The radius of curvature, p, of 7 GeV/c is 11.67 m for the mag-          netic field of 20 kilogauss perpendicular to the beam direction. The error of dp/p           depends on the measured track length; dp  __ 8p. ds                                         p0 .3H•l2           where p is the beam momentum in MeV/c, and H is the magnetic field in kilogauss,            and 1 is the track length in cm, and ds is the error of measurement in cm in the bubble            chamber. As seen in Fig. 2, the estimated value of ds is 130 um.               Figure 3 gives the distribution of the rout-mean-square residuals of the incident            and secondary tracks obtained from the helix fit. The valuesare taken in the scale of           film plane. The peak value is about 10 tm and is consistent with the value of ds           taking account the magnitude of the bubble chamber to the film, about 12. ( 60 )                                     Measuring Projector •                           •                            •  o ••                              ti • • 100 • •                ••                    ,•:%•          '~'ai•\50••• • •         ••   a                   C. ••                      ••• •, • •                •••••'4       •{~ •• 10 - '' ,•• • : -                     • .                                     ••• ••••,                       ••a•5 -•'~•-                       ••4•                   rit •• •                         • 3,4.••6;.                                         ,• •,. ••••••• •tj«°•~04,•4, •• ,• • •_4•                             •••• • •                             ••6•i°A•••                           ••••~I••t•,• ••• ••••                                                             IS•                                 ••• •1—• -                                     • • • •    050100 150           TRACK LENGTH(CM )          Fig. 2. Scatter plot of the measuring errors of measured radii (d p/ p) for the incident                 anti-protons of 7GeV/c under the magnetic field of 20 kilogauss. Solid line                  corresponds to ds=130 pm (see text).      The space resolution of measurement in the image plane is limited by the magnetic-  scale resolution of 50 µm/count which corresponds to 5 µm in the film plane. The   magnetic-scale resolution is considered to be at least comparable with or better than the   measurement error. The conclusion is that the three measuring projectors are not   necessarily satisfactory, but are useful for the practical purpose in the analysis of the   bubble-chamber films.       We are now undertaking to examine various causes of the errors appearing in   fitting the events to a physical hypothesis, and to improve the program treating the results   of measurements, and to add the semi-automatic measurement device. ( 61 )                                          S. YAMASHITA, S.  MATSUKI, and Y. MIYATAKE    I I I I I I----------------------------------------------------------------------------I.              RESIDUAL DISTRIBUTION 60—— 50 — ——                 40 — E—           zIn 30 —                  I-          0 d Z—  20 ——  10 — ——            s                    — S 0  E I I I I— I m 7-1 I I         0 10 20 30 40 50 60 70 RESI DUAL (Nm)                        Fig. 3. Residual distribution for the all tracks involved in the flour-prong events.                                  ACKNOWLEDGMENT               The authors are grateful to Prof. T. Kitagaki, Prof. T. Yanabu, and the late Prof.            Y. Uemura for helpful comments and encouragements, and are indebted the members           of high energy physics laboratories at Tohoku University and Tohoku Gakuin Uni-          versity for their kindly help for carrying out the studies. They also wish to acknowledge            the assistance of Miss Y. Izuo, Miss M. Kayahara, Miss H. Kitazume, and Miss            H. Shigemori in the extensive data processing. ( 62 )

Measuring Projector for the Analyses of Bubble-Chamber Films (Memorial Issue Dedicated to the Late Professor Yoshiaki Uemura)

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Measuring Projector for the Analyses of Bubble-Chamber Films (Memorial Issue Dedicated to the Late Professor Yoshiaki Uemura)

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