A high energy electron positron collider is proposed to complement the large hadron collider, LHC, which has started taking data at CERN, Geneva, Switzerland. Based on superconducting acceleration technology the International Linear Collider ILC is offering a mature proposal. It will deliver high luminosity electron positron collisions at 500 GeV upgradable to 1 TeV. Experimentation at such a collider presents many unique challenges, if the huge physics potential should be harvested efficiently. In this paper after a brief review of the state of the accelerator proposal the state of the preparation of the experimental program is discussed.

Colorless and crack-free single crystals of bismuth silicate (Bi₄Si₃O₁₂, BSO) scintillators have been grown by the vertical Bridgman method. Some segregation phases have been found to form on the surface and at the top of the crystals grown from both stoichiometric and off-stoichiometric melt compositions. The excitation and emission spectra are similar to BGO. The light output is 20% of BGO, giving energy resolution of 32% for 662 keV γ-rays (¹³⁷Cs). The decay constants are 2.4 ns (for 6% of intensity), 26 ns (12%) and 99 ns (82%). The radiation hardness against⁶⁰Co γ-rays was found about 10⁵–10⁶ rad at the emission peak of 480 nm for undoped and it was almost negligible up to 10⁷ rad for 0.2 at.% Ce doped crystals. We have also achieved a considerable improvement in the growth of large size crystals, offering the possible application in γ-ray detectors at high energies. Clear blocks with transverse/longitudinal dimensions as large as 25 mm/200 mm were produced with good reproducibility. The pulse height uniformity along the longitudinal axis is within ±2%. The scintillation characteristics are similar to those of small crystals.

The optical properties and radiation hardness of large-size PbWO₄:Y crystal grown with modified Bridgman method were investigated through characterization on the optical transmittance, X-ray excited luminescence, light yield and irradiation damage of series 24 × 24 × 24 mm³ block crystals cut from a long as-grown ingot. From the measuring results of the sequential small block samples it can be concluded that large-size modified Bridgman grown PbWO₄:Y crystals have excellent uniformity of optical properties and radiation hardness.

Single crystals of undoped PbFCl have been grown. The ionic conductivity of these crystals has been measured parallel and perpendicular to the crystallographicc-axis, and has been compared with the ionic conductivity of undoped β-PbF₂ and PbCl₂ single crystals.

According to Greenwood the crystal structures involved favour the presence of anion Frenkel defects. In spite of the fact that conductivity experiments on undoped materials are not conclusive, the present results, together with structural considerations, favour the presence of Schottky defects.

Lead fluoride chloride (PbFCl) crystal was grown by modified Bridgman method. The result of X-ray powder diffraction pattern (XRD) was well accordant with the data of JCPDS card. The transmittance spectrum was first reported without absorption band from 270 to 800 nm. Three emission bands were first observed at room temperature when excited by ultraviolet light.

Lead fluoride chloride (PbFCl) crystals with different F/Cl ratio were grown by modified Bridgman method. The excess of PbCl₂ is favorable to the crystallization of transparent ingot. X-ray powder diffraction analysis was used to identify the phases in PbFCl ingots. The transmittance spectra of the samples indicated that the presence of PbF₂ or PbCl₂ did not cause extra absorption bands in PbFCl crystals. F/Cl ratio strongly affected the number of emission bands and their peak positions in X-ray excited luminescence of PbFCl.

The luminescence spectra of PbFCl single crystal under the excitation of synchrotron radiation vacuum ultraviolet–ultra violet (VUV–UV) were investigated. The emission spectra of PbFCl single crystal show a broad violet band peaking at 400 nm having decreasing intensity with the rising temperature being from 20 to 293 K under the excitation of VUV–UV. A weak ultraviolet band peaking at 325 nm, which can be ascribed to the cation exciton emission of Pb²⁺, appears at 20 K under the excitation at wavelength shorter than 247 nm, but is completely quenched above 60 K. The violet band emission due to energy transfer from cation exciton was observed, which became more effective above 60 K. The luminescence in the violet band may be due to STE luminescence or is probably associated with the Pb²⁺ ion close to the Schottky-like defect.