Simulations of SST options (an update)‏ R D Parsons

Secondary optics in sim_telarray Simulation of secondary optics is possible within sim_telarray Curved focal planes are implemented by staggering of the pixels Mirror shapes must be included in the form of a polynomial Cross checks show it reliably recreates the results of other ray tracing programs

Telescope PSF Version 17 telescope (JS) found to have best performance of those tested Telescope has 4m primary and 2m secondary PSF does not degrade too significantly across the field of view Plate scale is however too large for our pixel size Telescope size must be scaled down (3.4m)‏

Camera Layout 1472 pixel camera Consists of 23, 64 channel MaPMTs Angular size of 0.2 deg Using super bi-alkali photo- cathodes Each pixel is 6.2mm Camera Effective size of 8.9 deg

4 Large (23m)‏ 23 Medium (12m)‏ 120 Small (3.4m sec optics)‏

Results (Oxford)‏ Improvements seen in effective area over E at high energies (> 3 TeV)‏ At 1 TeV effective area lost where DC SSTs would be triggering SecOpt (2 tels)‏ Array E (2 tels)‏ Loss in angular resolution over array E is minimal, especially if harder cuts are used SecOpt (3 tels)‏

Array Layout Previous array found to have poor layout of telescopes Cost model was also probably a little optimistic A new simulation configuration has been suggested by Jim Hinton Containing 3 array layouts, all sharing the same LST and MST arrangement

Array Layout 4 23m LSTs and 25 12m MSTs at the array centre DC array , centre surrounded by 36 6m DC optics SSTs (green)‏ SO_1, centre surrounded by 88 3.4m SC optics SSTs (red)‏ SO_2, centre surrounded by 92 3.4m SC optics SSTs (magenta)‏

Array Layout SO_1 aims to have a similar effective are a as DC array (~5 km2), but should have an improved angular resolution due to the smaller spacing of telescopes SO_2 attempts to maximise effective area (~10 km2) while keeping the telescope spacing similar to that of the DC option The comparison between these two SO arrays and the DC array, should help us understand angular resolution vs. effective area tradeoffs

Improvements to electronics Previous SC telescope simulations have included unrealistic (and pessimistic) simulations of the camera electronics and image analysis Improvements and investigations need to be made before SC optics can be included in prod 2 simulations What needs improvement? FADC Readout window FADC sample rate Trigger threshold Tail cut level Something else?

Investigations into SO SSTs Simulations have been performed to find the optimum trigger threshold to the telescope FADC sampling rate reduced to 500MHz Two FADC window sizes will be investigated, 50 ns and 100 ns The effect of using pulse finding algorithms on these large window sizes will also be investigated Simulations adding these improvements and using the new array layout are underway

New Array Response SO_2 Some low stats simulations have been performed with the new layout Using a 50 ns gate length and no pulse finding DC SO_1 Plots made are pre-background rejection cuts 30 p.e. amplitude cuts and 2 telescope multiplicity cuts

Other SST options It has also been suggested that G-APDs may be used as a light sensor on a DC optic telescope (similar to FACT)‏ It should be possible to simulate such an arrangement within sim_telarray Detailed input required: QE of photosensor Angular response of sensor + cone Cost of sensor + cone, etc

Other SST options It is also possible to use G-APDs as the sensor in the secondary optics solution This would require a curved solid Winston cone surface Some simulations have been performed by Isabel Braun Again requires more detailed input for simulation in sim_telarray

Summary sim_telarray is able to simulate all the proposed designs for the SST Some early studies using SC optics have been performed, showing an increase in effective area above 3 TeV, with little effect on angular resolution Work on a more realistic study is underway, improving the array layout and simulating the electronics chain more accurately This work should produce results soon Before G-APD designs can be simulated within sim_telarray more input is required