Gregor Kramberger Jo ef Stefan Institute, Ljubljana on behalf of - PowerPoint PPT Presentation

Gregor Kramberger Jo žef Stefan Institute, Ljubljana on behalf of ATLAS HGTD group

 Motivation ◦ Imporatance of HGTD for offline analysis ◦ Luminosity meter/Beam monitor  HGTD design ◦ Location and rates ◦ Radiation environment  Sensors and electronics ◦ Problem of timing measurements ◦ Prototype results (source and test beam measurments) ◦ Radiation damage ◦ Electronics  Mechanical construction (modules and staves)  Conclusions 2 9/14/2017 G. Kramberger, ATLAS-HGTD, 26th Vertex Workshop, Las Caldas

8 c countrie ntries, 22 institutions tutions, >120 0 people involved ved 3 9/14/2017 G. Kramberger, ATLAS-HGTD, 26th Vertex Workshop, Las Caldas

 HL-LHC upgrade Phase II (2026->) ◦ number of pileup collisions will increase to 140-200 ◦ huge task to assign reconstructed particles to individual collisions and to extract interesting collisions ◦ Is there a way to separate vertices also not only in space but also in t time? on average ge 1.6-2.35 35 verti tices ces per mm At LHC the vertices are distributed GTD (Gaussian) with: s z =5 cm & s t =180 ps HGT Tracking detectors (ITk-pixel+strip) provide resolution of primary vertices in forward region typically >1 mm, which leads to merging of up to 7 collision vertices It is a task of the HGTD to provide timing resolution of around of 30 ps for minimum ionizing particles (60 ps/mip/layer). ITk 4 9/14/2017 G. Kramberger, ATLAS-HGTD, 26th Vertex Workshop, Las Caldas

Timing “layer” inserted between tracking detectors and EM calorimeter HGTD TD A goal for the future – to have also tracking in 4D 5 9/14/2017 G. Kramberger, ATLAS-HGTD, 26th Vertex Workshop, Las Caldas

Timing “layer” inserted between tracking detectors and EM calorimeter A goal for the future – to have also tracking in 4D (superb “ Vertexing ”) 6 9/14/2017 G. Kramberger, ATLAS-HGTD, 26th Vertex Workshop, Las Caldas

Offline e capabilities es - full simulation: cleaning up the pile up contamination (track fraction) in jets (at 1.6 collisions/mm from  14% to 3%) up to 15 % improvement of lepton isolation in high pileup environment  20% improvement in forward PU jet suppression signal efficiency – larger fraction of Hard  Scatter jets Resolving primary vertex -> Potential large gains in b-tagging (up to factor of 2), pileup  tracks contamination 7 9/14/2017 G. Kramberger, ATLAS-HGTD, 26th Vertex Workshop, Las Caldas

Initial plans – > include HGTD in L0 trigger ger to separate HS jets from pileup ones (a HS jet is collimated both in time and space) Participation in L0 trigger decision (VBF jet trigger) are not considered dered in the baseline, except using “luminosity mode” for triggering minimum bias events Luminosity meter – measuring the total number of hits in HGTD: bunch per bunch measurement (online)  no afterglow problems  easier to spot drifts  Tasks to explore: amount of data  robust algorithms:  acceptance selection ◦ linearity ◦ <10 -4 stat. uncertainty @ m =200 Beam conditi tion on monitor oring: Timing distribution of hits can be exploited to monitor the cavities performance  t 0 re-synchronization : monitor expected timing with measured one for each BCiD (drift)  8 9/14/2017 G. Kramberger, ATLAS-HGTD, 26th Vertex Workshop, Las Caldas

cleaning pile up contamination Track isolati tion on efficienc ency for electrons rons HGTD-Si: Initial studies included variety of sensors, but  4 la layers of Silicon pixel/p /pad ad detec tectors tors due to required compactness the choice was (studied also option with W-layers/preshower not limited to Silicon. considered as baseline HGTD-SiW) A desired timing resolution of the detector is  around 30 30 ps ps – a single layer resolution of 60 ps for mip particles –> “making HL - LHC pileup LHC like” 9 9/14/2017 G. Kramberger, ATLAS-HGTD, 26th Vertex Workshop, Las Caldas

5 cm BPE moderator required to shield ITk/HGTD from neutrons – lots of effort in simulation and design (“optimized” design shown) 10 9/14/2017 G. Kramberger, ATLAS-HGTD, 26th Vertex Workshop, Las Caldas

https://twiki.cern.ch/twiki/pub/AtlasPublic/LArHGTDPublicPlots/Radiation_IDR_last.pdf Note that ratio od charged hadrons/neutrons in NIEL varies with radii: NIEL p /NIEL n~1 @ R=12 cm NIEL p /NIEL n~0.2 @ R=40 cm F eq,max =6 ∙ 10 15 cm -2 Safety factors: x1.5 for fluence and x2.25 for TID (electronics) TID max =4 MGy 11 9/14/2017 G. Kramberger, ATLAS-HGTD, 26th Vertex Workshop, Las Caldas

Hit rates determine the cell size (# channels/electronics) – occupancy < 10% required 1.3x1.3 mm 2 pixels are compromise between: number of channels  pixel capacitance – noise/jitter performance  inefficient area around each LGAD cell  12 9/14/2017 G. Kramberger, ATLAS-HGTD, 26th Vertex Workshop, Las Caldas

Several detector options (all Si) investigated: HVCMOS, PIN diodes and LGADs. We  focused our efforts to LGADs. Low Gain Avalanche Detectors: seem to fulfil the requirements (radiation hardness?) and  is the only technology having the required maturity and interest. Gain depends on doping of the Landau fluctuations multiplication layer. s  s  s 2 2 2 t elec Landau s  s  s  s 2 2 2 2 elec TDC TW jitter t s rise ~ jitter S / N Gain mip  I e , h thickness Not only LGADs – what is required are thin LGADs (50 m m): We want to have fast rise time -> small jitter er • High gain with proper electronics design also leads to high S/N -> small l jitter • Thin detectors minimize time walk (short drift and saturated drift velocity ~ 1 ns) – smaller effect of • “Landau” fluctuations Thinner detector improve radiation hardness (less leakage, better electric field profile) • 13 9/14/2017 G. Kramberger, ATLAS-HGTD, 26th Vertex Workshop, Las Caldas

LGADs have so far been produced by CNM (several runs, RD50), FBK and HPK all proving to work well and can provide the quantities needed for HGTD in time. Most studies performed on CNM and HPK LGADs CNM several runs (R9088 most studied, 3 different doses , 3 different structures )  HPK ECX20840 run ( 4 different doses , 2 different structures )  50,80 m m thick CNM HPK diffe ffere rent 45 m m thick dopin ing g doses es 1.3x1.3 mm 2 C=2pF https://indico.cern.ch/event/637212/contributions/2608660/attachments/1471120/2276430/Kramberger-HPK.pdf 14 9/14/2017 G. Kramberger, ATLAS-HGTD, 26th Vertex Workshop, Las Caldas

Timing resolution of these sensors (R9088) was shown to be very good – 26 ps/layer for mip particles! wideband amplifiers 350 MHz (UCSC) used DUTs Quartz ( Č photons) +SiPM 20 ps resolution Gain=40 2 ns Constant Fraction Discrimination N. Cartiglia et al., NIM A850 (2007) 83. https://doi.org/10.1016/j.nima.2017.01.021 15 9/14/2017 G. Kramberger, ATLAS-HGTD, 26th Vertex Workshop, Las Caldas

For high gain Landau fluctuations related time walk dominates the resolution – noise  jitter is not so important Besides high gain also velocity has to be close to saturated <E>=3 V/ m m to make signal  as short as possible and minimize the effect of Landau fluctuations Landau fluctuations (not correctable) contribute ~25 ps for 50 m m detector  http://arxiv.org/abs/1707.04961 90 Sr UCSC setup up 90 Sing ngle e Pads ds TEST BEAM – Sing ngle e Pads ds TEST BEAM – Mini nimization ation of 2x2 array ay dead ad area ea @ same me (CNM NM – R9088) 8) HV performa mance nce is cruci cial al 16 9/14/2017 G. Kramberger, ATLAS-HGTD, 26th Vertex Workshop, Las Caldas

Gain degrades with fluence, due to loss of doping in multiplication layer.  “Breakdown” of the device is shifting to higher bias voltages with irradiations  medium dopin ing g od p + layer (1.9e13 cm -2 ) https://indico.cern.ch/event/587631/contributions/2471705/ Radia iati tion on damage mage and gain in: F eq <10 15 cm -2 : reduction of the gain due to acceptor removal in multiplication layer (smaller slope in Q-V)  10 15 cm -2 < F eq <2 ∙ 10 15 cm -2 : substantial multiplication visible only at highest voltages  F eq >2 ∙ 10 15 cm -2 : no difference between LGAD and PIN – bulk multiplication seen in both  Reduction of gain after charged hadron is larger (at the same NIEL) than for neutron irradiations. 17 9/14/2017 G. Kramberger, ATLAS-HGTD, 26th Vertex Workshop, Las Caldas

90 Sr UCSC setup up - Sing ngle e Pads ds TEST BEAM – Sing ngle e Pads ds 90 20 20 ke ke/50 m m http://arxiv.org/abs/1707.04961 J. Lange et al., JINST 12 (2017), P05003 With irradiations the required bias voltage for gain increases (above <E>=3 V/ m m the  velocity is almost saturated) -> the gain becomes directly related to time resolution (providing the noise level doesn’t change) At highest fluences trapping and charge multiplication in bulk lead to faster signal, hence  better timing resolution at the same gain as for the highest fluences. Opti timi miza zation ion of interl terlinked: nked: timing ming reso solut ution on, , detec tecti tion n effi fici cienc ency, y, nois ise occu ccupanc ncy is very ry challe lengi nging ng for r HGTD TD. 18 9/14/2017 G. Kramberger, ATLAS-HGTD, 26th Vertex Workshop, Las Caldas