Tungsten and Optics

摘要

The ESA INTErnational Gamma Ray Astrophysical Laboratory (INTEGRAL) satellite is the largest Gamma-Ray Astrophysics mission foreseen for this decade. Since its selection in 1994, three very innovative technologies were identified to achieve the INTEGRAL scientific goals: new generation Solid State Detectors, Active Veto Systems and Spatial Signal Multiplexing Systems. The high energy instruments of the mission, IBIS, SPI and JEM-X, have been developed by using the above referred technologies. The Grupo de Astronomia y Ciencias del Espacio (GACE) of the University of Valencia was chosen as the responsible to design and develop the Spatial Signal Multiplexing Systems (Coded Masks) for the three instruments, appointing the Spanish company SENER as the Prime Industrial Contractor. During the early design phase (1994-96) different materials were considered to modulate the high energy signals. Tungsten was selected as the optimum material for implementing the codes due to both its high density and large atomic number that provide the required stopping power. Codes follow HURA and MURA patterns, being the total mass of W used of around 280 kg. The scope of this paper is to summarise the milestones of the development programme carried out from 1994 until now, once the Flight Models have been manufactured, tested, delivered and mounted on the INTEGRAL satellite at Alenia and CNES (Oct/Nov 2000). We pay special attention to describing the complex Masks Themoelastic Designs, involving W coupled to composites and Ti. Mask Assemblies stability was tested in a wide range of temperatures (-80℃ +40℃) and mechanical stress (12g) at INTA facilities for Flight Qualification.