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[en] Since the 1st generation experiment, E89-009, which was successfully carried out as a pilot experiment of (e,e'K+) hypernuclear spectroscopy at JLab Hall C in 2000, precision hypernuclear spectroscopy by the (e,e'K+) reactions made considerable progress. It has evolved to the 2nd generation experiment, E01-011, in which a newly constructed high resolution kaon spectrometer (HKS) was installed and the 'Tilt method' was adopted in order to suppress large electromagnetic background and to run with high luminosity. Preliminary high-resolution spectra of ⁷_ΛHe and ²⁸_ΛAl together with that of ¹²_ΛB that achieved resolution better than 500 keV(FWHM) were obtained. The third generation experiment, E05-115, has completed data taking with an experimental setup combining a new splitter magnet, high resolution electron spectrometer (HES) and the HKS used in the 2nd generation experiment. The data were accumulated with targets of ⁷Li, ⁹Be, ¹⁰B, ¹²C and ⁵²Cr as well as with those of CH₂ and H₂O for calibration. The analysis is under way with particular emphasis of determining precision absolute hypernuclear masses. In this article, hypernuclear spectroscopy program in the wide mass range at JLab Hall C that has undergone three generation is described.

[en] Aerogel and water Čherenkov detectors were employed to tag kaons for a Λ hypernuclear spectroscopic experiment which used the (e,e′K⁺) reaction in experimental Hall C at Jefferson Lab (JLab E05-115). Fringe fields from the kaon spectrometer magnet yielded ∼5 gauss at the photomultiplier tubes for these detectors. These fields, which could not be easily passively shielded, would result in a lowered kaon detection efficiency if not mitigated. A bucking coil was placed on each photomultiplier tube to actively cancel this magnetic field, thus recovering kaon detection efficiency. -- Highlights: •Bucking coil was developed to cancel a magnetic field for a photomultiplier tube. •A gain reduction of the PMT due to magnetic fields was carefully studied. •Bucking coil conditions were optimized to recover the gain of the PMT. •Bucking coils implemented in a hypernuclear experiment worked well

[en] A Λ hypernuclear spectroscopic experiment, JLab E05-115 was performed at JLab Hall-C in 2009 by the (e, e′K⁺) reaction. Data of Λ hypernuclei with mass numbers from A = 7 to A = 52 were successfully taken, and the analyses are in progress. A polyethylene (CH₂) target was used as a proton target to calibrate energy scales, and to study elementary process of the p(e, e′K⁺)Λ, Σ⁰ reaction. A preliminary differential cross section of K⁺Λ electro-production at low Q²[∼0.01 (GeV/c)²] and at small kaon angles (cosθ^CM_K ∼0.97) is reported in the present article. (author)