Comprehensive study and optimized redesign of the cern's antiproton decelerator target

Resum

The Antiproton Decelerator Target (AD-Target) is a unique device responsible for the production of antiprotons at the European Organization for Nuclear Research (CERN). During operation, intense 26 GeV energy proton beams are impacted into its core, made of a 3 mm diameter rod of a high density material such as iridium, creating secondary particles -including antiprotons- from the nuclear reactions induced in its interior. This thesis delves into the characteristics of antiproton production and in particular in the mechanical response of the target core material, which is exposed to a rise of temperature of approximate 2000 degrees Celsius in less than 0.5 microseconds each time is impacted by the primary proton beam. A coupled numerical-experimental approach has been applied for this purpose. Specific computational tools, called hydrocodes, have been used for simulating the extreme dynamic response taking place in the target core and its containing graphite matrix, indicating their potential damage and fragmentation as a result of a high frequency radial compressive-to-tensile pressure wave generated after each proton beam impact. A challenging first-of-its-kind experiment called HRMT27 was carried out. Several rods of high density materials, candidate for a future optimized target design, such as Ir, W, W-La, Mo, TZM and Ta were brought to equivalent dynamic conditions as reached in the AD-Target core by impacting them with 440 GeV proton beams using the HiRadMat facility. Online instrumentation was used to measure the predicted radial wave, confirming the accuracy of the hydrocode simulations. All of the irradiated target materials except Ta showed internal cracking from conditions 5-7 times below the present in the AD-Target while the latter apparently survived. Lessons learned are applied for proposing a new optimized target design, including a pressurized-air cooling system, Ta core configuration, and a containing matrix made of expanded graphite (EG). Computational Fluid Dynamic and Structural Finite Element analyses have been carried out to validate the new cooling system and fatigue life of the target assembly. A first prototype of the target core and its containing EG matrix has been built. These activities lead the way into manufacturing a new set of antiproton targets to guarantee antiproton physics at CERN during next decades of operation.