Construction Schedule

The construction of the spectrometer system is under way almost as scheduled.

The design of the spectrometer magnets and investigation on the installation procedure have been intensively carried out in collaboration with the Jlab engineering group. Magnets, a power supply for the 210-ton dipole magnet, vacuum chambers are under construction by Mitsubishi electric Co in Kobe, Japan. It is scheduled to be completed and assembled at the factory in the spring of 2002. The collaborators as well as the Jlab engineers plan to join the assembling at the factory so that the procedure at Jlab is examined. Intensive measurement of the 3D field maps will be conducted after the assembly at the factory prior to their shipping to Jlab. The field map data will be used to tune the analysis program of the HKS spectrometer. It is scheduled that the company is ready to ship the HKS spectrometer magnets to Jlab anytime in the fall-winter of 2002.

Basic designs for the most of detectors have been also completed. The drift chambers for the kaon and electron arms are now under construction among the collaborating institutions. Final R&D experiments for the TOF hodoscopes and Cerenkov counters are scheduled to run in December, 2001 at KEK 12-GeV PS using unseparated electron, pion and proton beams. All the detector components will be ready to be brought to Jlab by the end of 2002.

The E01-011 collaboration group will be ready to stage the experimental setup in whichever the experimental hall available, either Hall C or Hall A, at the beginning of 2003.

The present construction schedule of the system is summarized in figure 39.

図 1: Scatter electron angular distribution of the virtual photons with the $^{12}$C target

図 2: Angular distribution of kaon in the $^{12}$C(e,e'K$^+$) $^{12}_{\Lambda }$B reaction.

図 3: Hypernuclear yield of $^{12}_{\Lambda }$B$_{gr}$ as a function of the beam energy assuming scattered electrons are measured at E$_{e}$ = 0.285 GeV.

図 4: Plan view of the high-resolution kaon spectrometer (HKS) and Enge spectrometer for the E01-011 experiment.

図 5: Enge tilt angle dependence of the expected rate. The beam current of 30$\mu$A and carbon target 100 mg/cm$^2$ are assumed. Figure of merit is defined as $S^2/N$, where $S$ is number of electrons associated with virtual photon and $N$ the sum of bremstrahlung electrons and M$\phi$ller scattering electrons.

図 6: Expected Hall C setup of the HKS and Enge spectrometer. The installation can be compatible with the G0 setup.

図 7: Momentum correlation between kaon arm and electron arm for hyperons and hypernuclei production reaction.

図 8: Beam profile at each detector (Drift chamber, TOF wall, Aerogel Cerenkov, Lucite (Water) Cerenkov).

図 9: Momentum dependence of the solid angle of HKS.

図 10: Beam profile at collimator, Q1 entrance and exit, Q2 entrance and exit, and dipole entrance.

図 11: Two dimensional plot for angular acceptance of HKS for each momentum. Each ring corresponds to 0$^\circ$, 1$^\circ$ and so on.

図 12: Chamber spatial resolution dependence of the momentum resolution of the HKS obtained with the GEANT simulation (top). The solid line and dashed lines are respectively for with and without multiple scattering effects. The contributions of the chamber spatial resolution to the angular resolution are plotted (bottom). Red lines are for vertical and blue for horizontal.

図 13: Side and front views of the Q1 magnet. Unit of size is millimeter.

図 14: Front and side views of the Q2 magnet. Unit of size is millimeter.

図 15: Calculated excitation curves for Q1 and Q2 magnets. Integrated field gradient (T/m$\cdot$m) and field gradient (T/m) are shown for Q1 and Q2. The required integral field gradient for Q1 and Q2 are plotted as closed circles.

図 16: Cross sections of D magnet. Unit of size is millimeter.

図 17: The uniformity of the dipole magnetic field calculated with Poisson. Total current was varied from 10000-65000A to have the averaged magnetic field of 0.25 - 1.44 T. The uniformity of $< 1 \times 10^{-3}$ is achieved in the region of $\pm$40cm from the beam center.

図 18: Cross section of the Q1, Q2 and D magnets. Vacuum chambers are connected from the splitter magnet through Q1, Q2 and D magnets to the extension vacuum box. It can be seen that the dipole yoke has a cut for photon line.

図 19: Layer configuration of the HKS drift chamber.

図 20: One layer board (u plane) of the HKS drift chamber. Anode wires are tilted with an angle of 30 degrees and their signals are amplified and discriminated with Nanometrics 277N boards.

図 21: Beam's eye view of HTF1X.

図 22: Beam's eye view and top view of HTF1Y.

図 23: Schematic of the aerogel detector design.

図 24: Simulated average number of photoelectrons as a function of track position for pions with 1.2 GeV/$c$ momentum. (a) Vertical distribution. (b) Horizontal (HKS bending direction) distribution. (c) & (d) Vertical distribution for top and bottom tube, respectively.

図 25: Simulated trigger efficiencies. (a) Full line: total number of photoelectrons without any cut. Dashed line: total number of photoelectrons for coincidence trigger between top and bottom tube: ( $N_{p.e.}^{top}>2$).and.( $N_{p.e.}^{bottom}>2$) (b) Pion inefficiency (fraction of pions not setting the veto) as a function of a threshold on the total number of photoelectrons. (c) Pion inefficiency (fraction of pions not setting the veto) as a function of common threshold on top and bottom tube ( $N_{p.e.}^{top}>thr.$).and.( $N_{p.e.}^{bottom}>thr.$)

図 26: Momentum dependence of the number of photoelectron for Cerenkov counter for various refraction index (water: n = 1.33, lucite: n = 1.48, PVT: n = 1.58). The number of photo electrons per path length in the radiator is calculated assuming the efficiency of the light correction and quantum efficiency of PMT are 90% and 27%, respectively.

図 27: Simulation results of ADC spectra for water and acryl (lucite) Cerenkov counters. For acryl counter, total reflection and normal types were studied.

図 28: The optical features for the tilted Enge spectrometer obtained by ray-trace simulation. Top-left) vertical scattering angle ($\theta _{e'}$ in degrees), top-right) horizontal scattering angle ($\phi _{e'}$ in degrees), center-left) correlation between deviation from the central momentum (abscissa $dp$ in MeV/$c$) and horizontal scattered electron angle at the target ($Xp_i$ in mrad), center-right) correlation between $dp$ in MeV/$c$ and vertical scattered electron angle at the target ($Yp_i$ in mrad), bottom-left) correlation between $Xp_i$ vs $Yp_i$ and bottom-right) $dp$ distribution for the Enge acceptance.

図 29: The correlations between deviation from the central momentum ($dp$) and observable quantities on the Enge focal plane. top-left) horizontal position vs $dp$, top-right) vertical position vs $dp$, bottom-left) horizontal angle vs $dp$ and bottom-right) vertical angle vs $dp$.

図 30: The correlation between the horizontal position ($X_f$) and vertical position ($Y_f$) on the focal plane. Units are in centimeter.

図 31: Enge resolution for various position and angular resolution. The solid lines shows the resolution when $\sigma$X' and $\sigma$Y' are changed at the same time. Dashed line and dotted line shows the resolution when $\sigma$X' is fixed and only $\sigma$Y' varies.

図 32: The scattered electron image at the entrance of the Enge spectrometer.

図 33: The various plots for sieve slit holes' images

図 34: Conceptual drawing of the honeycomb drift chamber.

図 35: Isochrome drift lines for one honeycomb cell.

図 36: Beam's eye view of Enge hodoscope.

図 37: Trigger logic for E01-011 experiment.

図 38: Dump line required at Hall C.

図 39: Construction schedule. The green line refers to design phase, red one fabrication, blue one assembly and magenta one indicates the final tune.