Abstract
The CMS detector has been designed and realized to cope with an integrated luminosity of about \(\mathscr {L}=300\) fb\(^{-1}\) with some margin and an instantaneous luminosity of \(\mathscr {L}{\sim } 10^{34}\,\mathrm{cm}^{-2}\mathrm {s}^{-1}\).
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Notes
- 1.
Pile-up: number of proton-proton collisions in a single bunch crossing: \( \langle PU \rangle \) \(=\) 20 (LHC design); >50 (LHC reality); 200 (HL-LHC expectation).
- 2.
Often simply called Brems.
- 3.
3D tool adopting a non-simulative, parametrization-driven approach to tracker performance evaluation, taking e.g. multiple scattering as measurement error into account. It has been wetted against full simulation but it always provides the best case performance being independent of specific tracking algorithms. TKLayout runs more than 100 times faster than full simulation.
- 4.
2S = Strips+Strips sensors; PS = Pixel+Strips sensors.
- 5.
In the order of 0.2 x/X\(_0\) in the range \(1<|\eta | <2.5\).
- 6.
Interesting fact: The ‘binary’ SSA chip features two comparator thresholds, namely 0.4 and 1.5 MIPs, enabling to distinguish MIPs and highly ionising particles, a possible signature for a hypothetical long lived stable particle.
- 7.
Unfortunately, the trick, used in Phase I to move them out of the tracking volume does not work any more with tracking up to \(|\eta |=4\) – the whole volume is dedicated to tracking.
- 8.
Both plots do not account for the material of services, e.g. connectors or manifolds outside the TK volume.
- 9.
Establishing a communication line between the two module/sensor ends would be an alternative but the corresponding R&D to establish this with Through Silicon Vias TSV proved to be a not yet mature technology.
- 10.
Data from multiple sources are routed through a multiplexing network which directs all the data from an individual bunch crossing to a single processor.
- 11.
At the relevant fluences, depletion voltage (\(V_{FD}\)) is a more abstract concept.
- 12.
The R&D was successful but it is even more economic to implement the PA routing into the hybrids.
- 13.
The on-chip comparator has no cluster algorithm but works individually for each channel. No centre-of-charge can be applied since the smaller signals are simply not recorded; resulting in binary position resolution \(\sigma _x = \frac{pitch}{\sqrt{12}}\).
- 14.
This non-Gaussian, also called anomalous, noise exists for the p-in-n sensors in this campaign. It is probably that this could be overcome with an adapted strips design but it still looks like, that n-in-p sensors with \(p^+\)-stops have more margin than p-in-n.
- 15.
Device simulations [316] have shown that irradiated p-in-n strip sensors develop high electric fields at the strip edges, intensifying with increasing accumulation of oxide charge. The electric fields around the n-strips in n-in-p sensors are instead reduced by higher oxide charge, which makes them more robust with respect to effects, such as breakdown, noise or micro-discharge after heavy irradiation with charged particles.
- 16.
The oxygen content of dd-FZ is already very high due to the high temperature treatment. Still, the oxygen concentration in mCz is one order of magnitude higher and due to the crystal growth process in the magnetic field more homogeneous.
- 17.
As reminder, low resistivity \(\rho \) would result in a high starting depletion voltage which for n-in-p sensors only increase with radiation.
- 18.
Also polysilicon is an option.
- 19.
Only dd-FZ exists, the deep diffusion process is not available for mCz. Although some companies might explore dd for mCz.
- 20.
Time-over-threshold readout will be used and centre-of-charge calculation is possible; different to the binary readout in the Outer Tracker.
- 21.
Final active thickness still to be optimized – 130 \(\upmu \)m is just an example.
- 22.
E.g. BCB Benzocyclobutene deposition and parylene coating is being investigated.
- 23.
In case the layout would be enlarged to cover up to \(|\eta |\,=\, 4\) the expected levels would increase to even \(\varPhi _\mathrm{eq}\,=\, 10^{17}~n_{1\mathrm{MeV}}/\mathrm{cm}^{2}\).
- 24.
Electrons, positrons from pair production and \(\gamma \)s from Bremsstrahlung.
- 25.
Potentially the BH part will be in the cold volume too, to ease thermal interfaces.
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Hartmann, F. (2017). The Design of the CMS Upgrade Tracker and the CMS High Granularity Forward Calorimeter Equipped with Silicon Sensors for the HL-LHC. In: Evolution of Silicon Sensor Technology in Particle Physics. Springer Tracts in Modern Physics, vol 275. Springer, Cham. https://doi.org/10.1007/978-3-319-64436-3_7
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