Monday 7 November 2016

Linac 4 reached its energy goal

Linac 4 during its installation in 2015. This photo was taken as part of the 2015 Photowalk competition (Image: Federica Piccinni/CERN)

CERN’s new linear accelerator (Linac 4) has now accelerated a beam up to its design energy, 160 MeV. This important milestone of the accelerator’s commissioning phase took place on  25 October.

Linac 4 is scheduled to become the source of proton beams for the CERN accelerator complex, including the Large Hadron Collider (LHC) after the long shutdown in 2019-2020. It will replace the existing Linac 2 as the first link in the accelerator chain, which is currently accelerating protons at 50 MeV. The new 30-metre-long accelerator will accelerate hydrogen ions – protons surrounded by two electrons – at 160 MeV, before sending them to the Proton Synchrotron Booster. Here, the ions are stripped of their two electrons to leave only the protons that will be further accelerated before finishing their race in the LHC.

Linac 4 comprises four types of accelerating structures to bring particles in several stages to higher and higher energies. These accelerating structures have been commissioned one by one: in November 2013, the first hydrogen ion beam was accelerated to the energy of 3 MeV and two years after, the Linac 4 accelerator has reached an energy of 50 MeV – the energy Linac 2 runs at. Then, on the 1 July 2016, it crossed the 100 MeV threshold.


via CERN: Updates for the general public
http://home.cern/about/updates/2016/11/linac-4-reached-its-energy-goal

Graphene drums show their colors

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Graphene membranes hold potential for many applications, for example gas impermeable membranes, MEMS and NEMS pressure sensors, water filtration, high sensitivity ultrasonic speakers and microphones, quantum memories, and for fundamental scientific studies of opto- and nano-mechanics. Reliable large-scale characterization of graphene membranes has been elusive, because all known techniques actually affect the membrane during measurement, while also demanding costly equipment that does not allow parallel measurement of several membranes, hindering commercialization of graphene mechanical sensors.

A new method, developed at the Kavli Institute of Nanoscience at Delft University in the Netherlands, uses simple optical interference measured under a modified microscope to resolve the deflection of graphene membranes. The deflection is measured by looking at the optical interference between the light reflected off the drum and a silicon substrate. A simple fitting algorithm is applied to extract the exact deflection at the center of the drum.

The novel method is used to study diffusion of air through double-layer graphene membranes. Defect-free single layer graphene (SLG) would make a completely impermeable gas membrane if it were perfect, however in real conditions any SLG has a significant amount of cracks and wrinkles, enough to quickly let trapped gases seep out. However, if two independently grown sheets of graphene are stacked on each other, then for the most part the defects of the two sheets do not overlap, yielding a much less permeable membrane.

Using Graphenea’s technique of making suspended graphene on cavities, the research team created a matrix of double-layer graphene (DLG) membranes. DLG, apart from providing better gas membranes, has a higher optical contrast than SLG, making the experiments easier. The scientists studied membrane deflection while filling and purging the microcavities with air. A little surprisingly, they found that the membranes have higher permeance for purging than they have for filling with air. The results indicate that there are more purging channels than filling ones, perhaps related to the graphene-substrate interface.

The latest results, published in the journal Nano Letters under the title “Colorimetry Technique for Scalable Characterization of Suspended Graphene”, provide insight into the mechanics of graphene membranes, especially in relation to gas permeation applications. At the same time, the paper discusses a new method of characterization that should prove to be useful for studying graphene membranes as they progress from the lab to the marketplace.

Figure: Graphene drum deflection under pressure (reprinted with permission from Nano Letters, DOI: 10.1021/acs.nanolett.6b02416. Copyright 2016 American Chemical Society).

About Graphenea

Graphenea, a leading graphene producer venture backed by Repsol, was established in 2010, and has since grown to be one of the world's largest providers of graphene. The company is headquartered at the nanotechnology cluster CIC nanoGune in San Sebastian, Spain and the MIT campus in Cambridge, MA Boston. Graphenea employs 22 people and exports graphene materials to more than 600 customers in 55 countries. The company has focused on constant improvement of graphene quality, becoming a supplier customers can rely on. Graphenea employs a team of skilled laboratory staff who have brought graphene production techniques to a new level. Graphenea produces CVD graphene wafers and graphene oxide. Graphenea partners with large multinationals to develop custom graphene materials for their applications. Its research agility and ability to keep pace with the progress of graphene science and technology has allowed Graphenea to become a core partner in the Graphene Flagship, a ten year project of the European Commission worth a billion euros. The company keeps a close relation with the world's leading scientists, regularly publishing scientific articles of the highest level and holds a strong patent portfolio.


via Graphenea

Inverted City Beneath Clouds

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Little Gem in jewel tones

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Space Science Image of the Week: Planetary nebula shows off its beautiful turquoise and rose quartz tones in new Hubble image
via ESA Space Science
http://www.esa.int/spaceinimages/Images/2016/11/Little_Gem_Nebula_shows_off_its_jewel_tones

Green process to make carbon fiber used in rocket nozzles gets patent

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A new, green process developed to make carbon fiber that forms ablative rocket nozzles and heat shields could be of interest to NASA, which has a dwindling stockpile of cellulose rayon fiber that dates back to the late 1990s.
via Science Daily
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