Several of us contributed to the development of the ATLAS Insertable B-Layer (IBL), which is now being integrated into the Pixel system for start-up in spring 2015. The IBL is very important to ATLAS physics in general and to our heavy flavor research in particular, as it will substantially improve the quality of impact parameter reconstruction for tracks close to the interaction point, and thereby improve the vertexing and b-tagging performance of ATLAS in a way that will remain robust against pileup and hardware failures in Run 2. From 2013 onward, Konstantin and Rui worked on testbeams for development of the planar pixel sensors and in quality assurance measurements of the staves. Martin carried out electrical and mechanical measurements of irradiated modules with flex cables, in collaboration with INFN Genova.
Neil and Martin are developing cables for on-stave transmission from the innermost pixel layers. This is a difficult but important task because placement at the heart of the ATLAS detector requires high speed, low mass, and extreme radiation tolerance. They have designed, fabricated, and irradiated several generations of prototypes and demonstrated that their kapton-based differential embedded microstrip geometry continues to meet bandwidth and materials specifications after 3x1016 800-MeV protons/cm2, 500 MRad gammas, or 1016 1-MeV neutrons/cm2. Neil presented their work to the ATLAS ITK (Upgrade Semiconductor Tracker) Working Group on 10 July 2014 and at the ITK General Meeting on 8 September 2014. It was further overviewed at the First Mini-workshop on Read-out, Data Transmission, Routing, and Layout on 29 July 2014. The UNM design competes favorably with all other design options. The next step for Neil and Martin (2015 and beyond) involves honing the specifications, fabricating further prototypes, irradiating and testing those, and selecting the final design. In the subsequent years we expect to lead the QA and related integration. Neil is writing a paper on the full spectrum of cable designs UNM has fabricated and systematically tested against radiation. He expects to submit this paper to NIM in 2015.
Our ATLAS Upgrade responsibilities include:
(1) Design of the calibration system of the ATLAS Forward Physics (AFP) detector (Martin and David). AFP will provide
precise measurements of the true energy of the partons, allowing unprecedented measurement of parton shower and
hadronization parameters. AFP data will complement the data used in Igor and Jessica's studies of central jet structure.
(2) Diamond Beam Monitor (DBM) services and integration (Martin and Aaron). UNM is specifying the Type 2 cables between
Patch Panels 2 and 1. Diamond technology will allow DBM to operate effectively in the extreme radiation environment
that will eventually compromise the MTBS and LUCID monitors. DBM will provide highly segmented spatial information to
complement the (likewise diamond-based) BCM's time segmented information.
(3) Development of the ATLAS IBL. With IBL, ATLAS track reconstruction will be
robust against pile-up and hard failures of modules in the other silicon layers, and the b tagging performance will be
improved. Martin and Qufei are responsible for measuring the impedance and strain characteristics, before and after irradiation
by us at LANSCE (see the section on Instrumentation below), of the custom cables that will connect the modules in the stave
of the IBL to the end of the barrel. Designing and testing these cables is challenging because of the simultaneous requirement
for high density and low mass. Their physical dimensions and flexibility require design and fabrication at UNM of custom fixtures
to assure that the radiation they receive in our tests at LANSCE is uniform. Martin completed the first set of measurements in late
Spring 2012 on a cable we had exposed to 2.74 x 101s 800-MeV protonsjcmz in December 2011. His measurement used time domain reflectometry
(TOR) with 25 ps risetime differential pulses to measure differential impedance on 56 pairs of signal and clock lines. He observed good
performance of the cable with differential impedances of 85 to 110 ohms on all pairs of lines. Also for IBL, Konstantin and Rui are developing
software as part of the stave and system testing program at CERN. In fall 2012 they will expand the effort to include related system testing of the DBM.
(4) Rui and Konstantin operated modules at a variety of voltage and temperature conditions, with both irradiated and unirradiated assemblies, in the March
and May 2012 ATLAS Planar Pixel Sensor (PPS) testbeams. PPS are one of the baseline technologies for the IBL. Rui and Konstantin are both authors on
the PPS test beam results paper now in preparation.