Performance studies of the final prototype for the CASTOR forward calorimeter at the CMS experiment

We present performance results of the final prototype for the CASTOR quartz-tungsten sampling calorimeter, to be installed in the very forward region of the CMS experiment at the LHC. The energy linearity and resolution, the uniformity, as well as the spatial resolution of the prototype to electromagnetic and hadronic showers are studied with $E=$ 10--200 GeV electrons, $E=$ 20--350 GeV pions, and $E=$ 50, 150 GeV muons in beam tests carried out at CERN/SPS in 2007

Alignment of the CMS tracker with LHC and cosmic ray data

© CERN 2014 for the benefit of the CMS collaboration, published under the terms of the Creative Commons Attribution 3.0 License by IOP Publishing Ltd and Sissa Medialab srl. Any further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation and DOI.The central component of the CMS detector is the largest silicon tracker ever built. The precise alignment of this complex device is a formidable challenge, and only achievable with a significant extension of the technologies routinely used for tracking detectors in the past. This article describes the full-scale alignment procedure as it is used during LHC operations. Among the specific features of the method are the simultaneous determination of up to 200 000 alignment parameters with tracks, the measurement of individual sensor curvature parameters, the control of systematic misalignment effects, and the implementation of the whole procedure in a multi-processor environment for high execution speed. Overall, the achieved statistical accuracy on the module alignment is found to be significantly better than 10μm

A custom setup for thermal conductivity measurements

Future detector systems have increasing demands on the performance of their mechanical support structures and cooling systems. Novel materials and cooling technics are developed and continuously improved in order to fulfil these requirements. To quantify the thermal performance of these materials, a custom thermal conductivity measurement setup was developed.The setup consists of two heat flux meter blocks between which the samples are clamped. Each of the blocks has six temperature sensors embedded at equally spaced positions that allow to measure the heat flux through as well as the temperature gradient across the sample. A resistive load on top of the upper block acts as a heat source whereas the bottom block is thermally coupled to a cooling plate which acts as the heat sink. In order to minimize heat exchange between the heat flux blocks and the ambient via convection and radiation, the setup is covered with a radiation shield and measurements are carried out in a vacuum.The contribution will describe the setup in detail, motivate its design aspects and highlight the commissioning and calibration procedure. The analysis method as well as selected results from the currently ongoing measurement campaigns will be presented

Radiation qualification of thermal interface materials for detector cooling

Silicon sensor based particle detectors operated in an hadronic radiation environment need to be cooled to counteract the radiation induced leakage current and prevent thermal runaway. To achieve this most efficiently, a low thermal resistance is required between the detector modules and the cooling structures. In many cases dry thermal contacts are sufficient, but especially for large area contact so-called thermal interface materials (TIM) - of which many products are available on the market - are the preferred choice. However, in the use case for detector cooling there are many requirements, such as no liquid, no heat cure, low thermal impedance, no compression force, radiation hardness, making it more difficult to find a suitable TIM. An example use case is the cooling of the CMS Phase-2 Outer Tracker PS modules. Its entire underside of 5 x 13 cm must be thermally coupled to the mechanics. The current candidate materials are room temperature curing two component thermal gap fillers.The contribution will outline the measurements and highlight the results to qualify gap filler materials to the radiation dose expected for the lifetime of the CMS Outer Tracker. Three different types have been tested thermally and mechanically in this campaign.The thermal test setup determines the thermal conductivity of a test sample by measuring the temperature gradient with a controlled amount of heat flow through a sample. The development and calibration of this custom thermal conductivity measurement setup is detailed in a separate contribution to this conference.Mechanical tests are needed to ensure structural integrity of the thermal interface even when under some extent of thermal stress. Since the gap fillers can not be considered glues in classical sense, the standard lap shear and peel tests can't be used for qualification. Resembling the style of an ISO 4587 lap shear test, and an ISO 25217 mode-1 fracture test, test samples were made with a large 5 x 5 cm adhesion overlap using plasma cleaned carbon fibre plates to have a surface comparable to its intended use case. The testing method developed for this study will be presented and motivated.After testing of unirradiated samples, they have been irradiated to 600 kGy. The measured mechanical and thermal properties will be presented and the results before and after irradiation will be compared. We found that the gap filler material hardens significantly, however its thermal and adhesive properties are maintained. The hardening reduces the cohesion failure, leading to an increased mechanical strength

Thermal qualification of TEDD dees using infrared measurements

The instantaneous luminosity at LHC will increase by 2.5-4 times during Run-4 and Run-5 (HL-LHC). This poses new challenges for the tracker, such as higher pileup and track multiplicity. A new silicon tracking system designed to cope with the increased luminosity will be installed during the Phase-2 upgrade of the CMS detector. The new tracker has five double-disks (TEDD) in each endcap and each double-disk comprises four half disks (dees). A dee consists of two carbon fiber facings with carbon foam blocks sandwiched in between. The pixel strip (PS) and 2-strip (2S) silicon modules are mounted onto the surface of the dees.The PS and 2S modules need to be cooled efficiently to avoid thermal runaway. The carbon fiber facings function as cooling surfaces for the PS modules. Cooling pipes are embedded in the carbon foam blocks (which provide thermal contact between the facings and the pipes) to cool the dee facing. The 2S modules are cooled via aluminium inserts which connect the module to the cooling pipes. These inserts are embedded in the dee and protrude the facing.The integrity of the carbon foam blocks and the proper gluing of the carbon foam blocks and the 2S inserts with the carbon fiber facings play a crucial role in cooling the modules. Hence this needs to be validated during the reception test of the dees. A novel testing procedure using infrared imaging has been developed for this purpose and its capability has been demonstrated by thoroughly testing on prototype dees. The details of this procedure and measurement results of the prototype dees will be discussed in this poster

CMS Phase-2 Tracker endcap module cooling

For the high-luminosity LHC (HL-LHC), CMS will install a completely new silicon tracker. The future outer tracker will consist of two barrel parts and two endcaps (TEDD), one on each side. One endcap is made of five double-disks. One double disk is assembled from four half disks (Dees) on which the detector modules are mounted. The Dees are a highly embedded carbon fiber and foam sandwich with integrated cooling pipes and module positioning inserts.Due to its large and homogeneous power density, the PS detector modules need to be cooled from their entire underside of about 5 x 13 cm2 area. The carbon fiber facings of the Dees act as cooling surface. Carbon foam blocks are glued to the embedded cooling pipes and to the facing to facilitate the cooling of the Dee surface. The integrity of the carbon foam blocks and the proper gluing to the facing is important to establish the necessary cooling contact and needs to be validated during the Dee reception testing. A test system using infrared imaging has been built to discover non-conformities that would lead to a deteriorated cooling performance. The capabilities of this system has been demonstrated by extensively studying the Dee prototype. The infrared measurement setup will be presented and results obtained from measurements of prototypes will be discussed.One challenge is the identification of a thermal interface material (TIM) conforming to the requirements. The TIM must have a low thermal resistance even when used without pressure, re-workable in a potential module exchange, be radiation hard to the expected dose levels and an application technique has to be found, respecting the constrains of the handling of the fragile modules. Several candidate materials are being studied, with a focus on a two component self-curing thermal gap filler. The thermal performance and the mechanical properties of the TIM is being studied in preparation of an irradiation campaign to verify the material parameters at the end of life of the experiment. In this context a new thermal conductivity measurement setup has been built, commissioned and used to quantify the thermal performance of the candidate materials. The thermal conductivity measurement setup will be presented and the results will be discussed. The results of the mechanical testing will be presented as well as the plans and tests for the application of the material when integrating detector modules

Production of quartz plates for CMS-CASTOR Experiment

Light transmission rate performance of $102$ irradiated quartz samples was measured to select the best quartz plates for CMS-CASTOR calorimeter. All the produced quartz plates were originally used in a previous CERN experiment, DELPHI. Three different doses of $^{60}$Co source were used with the collaboration of PSI (Paul Scherrer Institute, Villigen PSI, Switzerland.) to study the transmission rate performance of the quartz samples after irradiation for different incident light, ranging from $250$ to $700$ nm in $5$ nm increasing steps. All samples show different decrease in the rate with wavelength for different doses. Three different steps were followed before irradiation to find out the best way of cleaning the original DELPHI Cu/Cr tracks on the samples. Results of these measurements presented here correspond to the quartz plates that will be used in one hadronic sector of CASTOR calorimeter until end of 2008. For the full calorimeter new quartz plates will be installed. We also present the light transmission rate of new quartz samples (fused silica) for $10$, $50$ and $100$ MRad dose levels. This activity was performed at CERN during the period from February to May of $2008$

Precision measurement of the structure of the CMS inner tracking system using nuclear interactions

The structure of the CMS inner tracking system has been studied using nuclear interactions of hadrons striking its material. Data from proton-proton collisions at a center-of-mass energy of 13 TeV recorded in 2015 at the LHC are used to reconstruct millions of secondary vertices from these nuclear interactions. Precise positions of the beam pipe and the inner tracking system elements, such as the pixel detector support tube, and barrel pixel detector inner shield and support rails, are determined using these vertices. These measurements are important for detector simulations, detector upgrades, and to identify any changes in the positions of inactive elements