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The initial attempts involved sprinkling molybdenum disulfide (MoS2) inside the bearing without disassembling it after cleaning. However, this method prevented uniform lubrication, leading to potential failures. The IAC mechanical team diligently refined the procedure, which included disassembling the bearings and replacing the cage by a technical polyamide cage.
This innovative approach significantly enhances efficiency; however, it comes at a higher cost due to high price of some technical polyamides such as Vespel. Additional research and testing have demonstrated that the pre-lubrication the bearing races with MoS2 significantly increases bearing life, although it involves a laborious process.
In recent years our focus has been on exploring more cost-effective material and how to improve bearing life.
This presentation discusses these techniques and the selected material for bearing preparation and presents the results of the latest cryogenic temperature life tests conducted on the produced bearings, along with the conclusions reached.
The Instrument Pre-Optics (IPO) is one of the HARMONI subsystems. It distributes the telescope light received from the adaptative optics systems. The main objective of the IPO is to format the field for the selected spatial scales feeding the Integral Field Unit (IFU). IPO is under the responsibility of the Institute of Astrophysics of the Canary Islands (IAC). This optical subsystem implements 30 Opto-mechanical mounts working at cryogenic temperatures. The mounts may be classified into two types based on the features of the optics they support: (1) Sprung Kinematic Mount (SKM) for flat mirrors, and (2) Thermally Compensated Kinematic Sprung Mounts (TCKSM) for power mirrors (toroidal mirrors, offaxis parabolas, and cameras). Designed to maintain optical alignment at cryogenic temperatures, the mounts maintain optical surface deformation within the limits specified by the error budget, ensuring compliance with requirements even worst-case scenarios.
This work describes the verification tests performed to the engineering models of the Opto-mechanical mounts of the IPO to validate compliance with the sub-system optical and mechanical requirements at both room and cryogenic temperatures.
The core of HARMONI is the Integral Field Spectrograph (IFS) which is composed of different subsystems including the IFS Pre-Optics (IPO). The IPO main objective is to take light from the focal plane relay system and reformat and condition it to be a suitable input for the rest of the instrument. The IPO in HARMONI includes the IFS Pre-Optics Fast Shutter (POFS), a mechanical cryogenic fast shutter which will be used with both the visible and infrared detectors. This mechanism has been designed to be fast and reliable and its design has already passed the Critical Design Review (CDR) but specific issues that require further analysis have been identified. The functioning of this element is a critical part in HARMONI and, consequently, a prototype has been used to analyze possible improvements in the CDR design and to perform extensive testing before the Final Design Review (FDR).
In this work we present the design of the IFS Pre-Optics Fast Shutter and the test results obtained with the prototype developed at the facilities of the Instituto de Astrofísica de Canarias (IAC).
A resonator is needed to enhance the weak signal originating from axion to photon conversion by the action of an external magnetic field. It is composed of ceramic plates and an electro-mechanical tuner. A fixed-plate prototype of a resonator has been manufactured and tested in an optical laboratory setup devised to excite it with a horn antenna and observe its resonant spectral feature from reflectivity measurements. A detailed description of the setup, the post-processing of the data and the observed resonant structure are treated in this work.
The focal plane mask wheel sits in the input focus of the cryostat. It provides 16 user-selectable positions for masks (28x40 mm) used in observation. The key driver for this mechanism is the high repeatability (±2.5 μm) required, equivalent to ~1mas in the input focal plane. The IAC has previously designed, manufactured, tested and put in operation cryogenic wheels with high repeatability; however, the challenge of obtaining a wheel with such repeatability requires testing new concepts of detent positioning systems.
The shutter allows for exposures shorter than the minimum read time of the near-IR detectors and is needed for any CCD observations with the visible cameras. A dual shutter design is needed to achieve the necessary open/close times (<20 ms), but this also provides some redundancy and a graceful failure mode for this critical device. To mitigate risks on the proper behaviour of a fast cryogenics shutter a prototype based on a simple concept has been manufactured. We present the design and results for the performed cryogenic tests of a mask wheel and a shutter prototypes that we have developed.
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