18 research outputs found
Structural Assembly from Phosphate to Germanophosphate by Applying Germanate as a Binder
National Natural Science Foundation of China [21201144, 21233004, 40972035]; Fundamental Research Funds for the Central Universities [2013121020]; Technological Innovation Platform of Fujian Province [2006L2003]Structural assembly from phosphate to germanophosphate by applying germanate as a binder has been achieved. Two isotypic porous compounds, K-3 [M-4(II)(HPO4)(2)][Ge2O(OH)(PO4)(4)]center dot xH(2)O (M-II = Fe, Cd; x = 2 for Fe and 3 for Cd, denoted as KFeGePO-1 and KCdGePO-1, respectively), contain a known transition-metal phosphate (TMPO) layer, (2)(infinity){[M-2(HPO4)(3)](2-)}, which is built from chains of trans-edge-sharing MO6 octahedra bridged by MO5 trigonal bipyramids that were further linked and decorated by phosphate tetrahedra. The layers are bound by infinite chains of GeO5(OH) octahedra, resulting in a 3D open-framework structure with 1D 12-ring channels that are occupied by K+ ions and water molecules. The curvature of the TMPO layers and shape of the 12-ring windows can be tuned by the transition metals because of their Jahn-Teller effect
Space charge limited avalanche growth in multigap resistive plate chambers
The ALICE TOF array will be built using the Multigap Resistive Plate Chamber(MRPC) configured as a double stack. Each stack contains 5 gas gaps with width of 250 μm. There has been an intense R&D effort to optimise this new detector to withstand the problems connected with the high level of radiation at the LHC. One clear outcome of the R&D is that the growth of the gas avalanche is strongly affected by space charge. The effect of the space charge is a decrease in the rate of change in gain with electric field; this allows more stable operation of this detector. We have measured the gain as a function of the electric field and also measured the ratio of the fast charge to the total charge produced in the gas gap. It is well established that RPCs built with 250 μm gas gap have a much superior performance than 2 mm gaps; we discuss and compare the performance of 250 μm gap MRPCs with 2 mm gap RPCs to show the importance of space-charge limitation of avalanche growth.
PACS: 29.40.Cs – 7.77.-n – 52.80.D
Design aspects and prototype test of a very precise TDC system implemented for the multigap RPC of the ALICE-TOF
The ALICE Time-of-Flight system will be a large area (150m**2) detector made by Multigap RPC (MRPC). T he time digitisation is based on the High Performance TDC chip (HPTDC). Tests carried out on board prototypes are discussed, emphasising the optimisation of the effective time resolution of the chip when working in its Very High Resolution Mode. Lab bench tests and test beam results show that a 20 ps resolution has been achieved