A Hydrogenated amorphous silicon detector for Space Weather Applications

The characteristics of a hydrogenated amorphous silicon (a-Si:H) detector are presented here for monitoring in space solar flares and the evolution of large energetic proton events up to hundreds of MeV. The a-Si:H presents an excellent radiation hardness and finds application in harsh radiation environments for medical purposes, for particle beam characterization and in space weather science and applications. The critical flux detection threshold for solar X rays, soft gamma rays, electrons and protons is discussed in detail.Comment: 32 pages, 13 figures, submitted to Experimental Astronom

Lipoma primitivo multiplo del mesocolon: una patologia rara

Gli Autori descrivono un caso di lipomatosi multipla del mesocolon e, dopo disamina della letteratura, ne esaminano le caratteristiche peculiari e discutono sulle difficoltà diagnostiche, sugli aspetti anatomopatologici e sul trattamento. La localizzazione intraaddominale del lipoma rappresenta infatti una patologia rara che può porre notevoli difficoltà diagnostiche. Poiché si tratta di tumori che prendono origine da cellule mesenchimali primitive e totipotenti, l’intervento chirurgico radicale è l’unica opzione terapeutica. La diagnosi di certezza spetta all’istologia per differenziare la lesione da altri tipi di tumore mesenchimale

L’emangioma capillare dello stomaco: una rara fonte di sanguinamento. Caso clinico

Gastric haemorrhages are common clinical emergencies which often directly involve the surgeon in diagnosis and treatment; among these, rare vascular neoplasms deserve particular attention. The Authors report a rare case of benign vascular tumour of the stomach, a capillary angioma. After a literature review they highlight the importance of specific exams to reveal these small neoformations which, generally, show up clinically with acute bleeding, which may be severe, and which may not be discovered if the clinical evaluation is not very detailed. The surgical excision supported by a frozen sections is the most effective treatmen

La complicanza perforativa da ingestione di corpi estranei alimentari: una patologia insidiosa sempre attuale. Nostra esperienza

The authors want to present five cases (from May 1999 to May 2009) of acute abdomen from perforation of the foreign body introduced with food. They highlight how the accidental ingestion is very common but the perforation is rare. The preoperative diagnosis, in these cases, is always very difficult and the radiological examinations are not always able to resolve the diagnostic doubt with other acute intestinal diseases that are responsible of perforation. Then, the surgery procedure is, necessarily, the only possible diagnostic and therapeutic means. The mortality and the morbility remain still high first of all for the delay in the diagnosis and the advanced age of patient

Fabrication of a hydrogenated amorphous silicon detector in 3-d geometry and preliminary test on planar prototypes

Hydrogenated amorphous silicon (a-Si:H) can be produced by plasma-enhanced chemical vapor deposition (PECVD) of SiH4 (silane) mixed with hydrogen. The resulting material shows outstanding radiation hardness properties and can be deposited on a wide variety of substrates. Devices employing a-Si:H technologies have been used to detect many different kinds of radiation, namely, minimum ionizing particles (MIPs), X-rays, neutrons, and ions, as well as low-energy protons and alphas. However, the detection of MIPs using planar a-Si:H diodes has proven difficult due to their unsatisfactory S/N ratio arising from a combination of high leakage current, high capacitance, and limited charge collection efficiency (50% at best for a 30 µm planar diode). To overcome these limitations, the 3D-SiAm collaboration proposes employing a 3D detector geometry. The use of vertical electrodes allows for a small collection distance to be maintained while preserving a large detector thickness for charge generation. The depletion voltage in this configuration can be kept below 400 V with a consequent reduction in the leakage current. In this paper, following a detailed description of the fabrication process, the results of the tests performed on the planar p-i-n structures made with ion implantation of the dopants and with carrier selective contacts are illustrated

High-Resolution Photoemission Study of Neutron-Induced Defects in Amorphous Hydrogenated Silicon Devices

In this paper, by means of high-resolution photoemission, soft X-ray absorption and atomic force microscopy, we investigate, for the first time, the mechanisms of damaging, induced by neutron source, and recovering (after annealing) of p-i-n detector devices based on hydrogenated amorphous silicon (a-Si:H). This investigation will be performed by mean of high-resolution photoemission, soft X-Ray absorption and atomic force microscopy. Due to dangling bonds, the amorphous silicon is a highly defective material. However, by hydrogenation it is possible to reduce the density of the defect by several orders of magnitude, using hydrogenation and this will allow its usage in radiation detector devices. The investigation of the damage induced by exposure to high energy irradiation and its microscopic origin is fundamental since the amount of defects determine the electronic properties of the a-Si:H. The comparison of the spectroscopic results on bare and irradiated samples shows an increased degree of disorder and a strong reduction of the Si-H bonds after irradiation. After annealing we observe a partial recovering of the Si-H bonds, reducing the disorder in the Si (possibly due to the lowering of the radiation-induced dangling bonds). Moreover, effects in the uppermost coating are also observed by spectroscopies