Design and Vertical Tests of SPS-series Double-Quarter Wave (DQW) Cavity Prototypes for the HL-LHC Crab Cavity System

Crab crossing is essential for high-luminosity colliders. The High Luminosity Large Hadron Collider (HL-LHC) will equip one of its Interaction Points (IP1) with Double-Quarter Wave (DQW) crab cavities. A DQW cavity is a new generation of deflecting RF cavities that stands out for its compactness and broad frequency separation between fundamental and first high-order modes. The deflecting kick is provided by its fundamental mode. Each HL-LHC DQW cavity shall provide a nominal deflecting voltage of 3.4 MV, although up to 5.0 MV may be required. A Proof-of-Principle (PoP) DQW cavity was limited by quench at 4.6 MV. This paper describes a new, highly optimized cavity, designated DQW SPS-series, which satisfies dimensional, cryogenic, manufacturing and impedance requirements for beam tests at SPS and operation in LHC. Two prototypes of this DQW SPS-series were fabricated by US industry and cold tested after following conventional SRF surface treatment. Both units outperformed the PoP cavity, reaching a deflecting voltage of 5.3-5.9 MV. This voltage - the highest reached by a DQW cavity - is well beyond the nominal voltage of 3.4 MV and may even operate at the ultimate voltage of 5.0MVwith sufficient margin. This paper covers fabrication, surface preparation and cryogenic RF test results and implications

Study of the Stabilization to the Nanometer Level of Mechanical Vibrations of the CLIC Main Beam

Original publication available at http://www.jacow.org/International audienceTo reach the design luminosity of CLIC, the movements of the quadrupoles should be limited to the nanometre level in order to limit the beam size and emittance growth. Below 1 Hz, the movements of the main beam quadrupoles will be corrected by a beambased feedback. But above 1 Hz, the quadrupoles should be mechanically stabilized. A collaboration effort is ongoing between several institutes to study the feasibility of the "nanostabilization" of the CLIC quadrupoles. The study described in this paper covers the characterization of independent measuring techniques including optical methods to detect nanometre sized displacements and analyze the vibrations. Actuators and feedback algorithms for sub-nanometre movements of magnets with a mass of more than 400 kg are being developed and tested. Input is given to the design of the quadrupole magnets, the supports and alignment system in order to limit the amplification of the vibration sources at resonant frequencies. A full scale mock-up integrating all these features is presently under design. Finally, a series of experiments in accelerator environments should demonstrate the feasibility of the nanometre stabilization

Challenging the negative images of Haiti at a pre-visit stage using visual online learning materials

Post-conflict destinations can struggle to attract visitors because of their negative image. Research addressing this remains limited. The same can be said about the education of tourists. This research paper contributes to the literature in both areas as it examines the proposition that the education of tourists at a pre-visit stage using online, game-based material could be effective in challenging the negative perception of these destinations. From a destination management point of view, this paper offers an alternative to existing promotional material as there is little evidence at the moment that existing strategies are effective. From a conceptual point of view, this paper contributes to the very limited academic research in Gamification by adding the fact that Gamification can be a very efficient tryvertising tool if using subtle and implicit marketing elements

Development of SRF Cavity Tuners for CERN

Superconducting RF cavity developments are currently on-going for new accelerator projects at CERN such as HIE ISOLDE and HL-LHC. Mechanical RF tuning systems are required to compensate cavity frequency shifts of the cavities due to temperature, mechanical, pressure and RF effects on the cavity geometry. A rich history and experience is available for such mechanical tuners developed for existing RF cavities. Design constraints in the context of HIE ISOLDE and HL-LHC such as required resolution, space limitation, reliability and maintainability have led to new concepts in the tuning mechanisms. This paper will discuss such new approaches, their performances and planned developments

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Clinical review: Functioning gonadotroph adenomas.

CONTEXT: Functioning gonadotroph adenomas (FGAs) are pituitary tumors secreting biologically active gonadotropins. The published literature includes only small case series or individual case reports. This review summarizes the published data on this rare entity and, based on them, suggests guidance on the follow-up of these patients. EVIDENCE ACQUISITION: A review of articles in English retrieved from the PubMed up to December 2013 was conducted. The following terms were used for the search: "functioning gonadotroph adenomas," "FSH secreting adenomas," "LH secreting adenomas," "gonadotroph adenomas," "ovarian hyperstimulation," "macroorchidism," "testicular enlargement," and "precocious puberty." EVIDENCE SYNTHESIS: All reported cases of FGA were assessed, and information on presenting manifestations, management approaches, and long-term outcome was reviewed. CONCLUSIONS: FGAs cause distinct manifestations and, based on the limited published literature, they are mostly macroadenomas. Their pathogenesis remains enigmatic. Systematic series on their optimal management are lacking, but the primary therapy remains surgical excision of the adenoma. Given the risk of recurrence, long-term clinical and imaging follow-up is needed, and radiotherapy may be required. There is little evidence that medical therapies are particularly helpful, certainly in terms of tumor control. Central registration would enhance our insight regarding their pathology and optimal management

The management of head-and-neck paragangliomas.

Paragangliomas (PGLs) are tumours originating from neural crest-derived cells situated in the region of the autonomic nervous system ganglia. Head-and-neck PGLs (HNPGLs) originate from the sympathetic and parasympathetic paraganglia, most frequently from the carotid bodies and jugular, tympanic and vagal paraganglia, and are usually non-catecholamine secreting. Familial PGLs are considered to be rare, but recently genetic syndromes including multiple PGLs and/or phaeochromocytomas have been more thoroughly characterised. Nowadays, genetic screening for the genes frequently implicated in both familial and sporadic cases is routinely being recommended. HNPGLs are mostly benign, generally slow-growing tumours. Continuous growth leads to the involvement of adjacent neurovascular structures with increased morbidity rates and treatment-related complications. Optimal management mostly depends on tumour location, local involvement of neurovascular structures, estimated malignancy risk, patient age and general health. Surgery is the only treatment option offering the chance of cure but with significant morbidity rates, so a more conservative approach is usually considered, especially in the more difficult cases. Radiotherapy (fractionated or stereotactic radiosurgery) leads to tumour growth arrest and symptomatic improvement in the short term in many cases, but the long-term consequences are unclear. Early detection is essential in order to increase the chance of cure with a lower morbidity rate. The constant improvement in diagnostic imaging, surgical and radiation techniques has led to a safer management of these tumours, but there are still many therapeutic challenges, and no treatment algorithm has been agreed upon until now. The management of HNPGLs requires a multidisciplinary effort addressing the genetic, surgical, radiotherapeutic, oncological, neurological and endocrinological implications. Further progress in the understanding of their pathogenesis will lead to more effective screening and earlier diagnosis, both critical to successful treatment

MANAGEMENT OF ENDOCRINE DISEASE: Pituitary tumour apoplexy.

Pituitary tumour apoplexy (PA) is a rare clinical syndrome that occurs as a result of acute haemorrhage and/or infarction within a frequently undiagnosed pituitary tumour. The sudden enlargement of the pituitary mass undergoing PA is responsible for a wide range of acute symptoms/signs (severe headache, visual loss, diplopia, hypopituitarism, impaired consciousness) which, together with the radiological evidence of a pituitary lesion, establish the diagnosis. The optimal care of PA requires involvement of a multidisciplinary team including endocrinologist, neurosurgeon, neuroophthalmologist and the management strategy depends on the clinical manifestations, as well as the presence of co-morbidities. Prompt surgical decompression is initially indicated in cases with severe or progressive impairment of the visual acuity or the visual fields or with altered mental state and leads to visual and neurological recovery in most of the patients. Patients with mild, stable clinical picture (including those with isolated ocular palsies) can be managed conservatively (support of fluid and electrolyte balance and stress doses of steroids in most cases) with favourable visual and neurological outcome. Frequent reassessment is mandatory because the clinical course can be unpredictable; if progression of symptoms occurs, later elective surgery is indicated and is beneficial, especially in terms of visual outcome. The endocrinological outcome is less favourable, irrespective of the treatment option, with many patients remaining on long-term replacement therapy. Despite the above guidelines, clear proof of optimal outcomes in the form of randomised controlled trials is lacking. Regrowth of the pituitary tumour years after a PA episode is possible and patients require long-term surveillance