Optimization of sub-relativistic co-propagating accelerating structures.

In this paper, novel optimization methodologies of sub-relativistic guided interaction structures for dielectric laser particle acceleration (DLA) are presented. In particular, we focus on co-propagating geometries based on slot waveguides in continuous wave (CW) operation, where the particle flow and the direction of propagation of the accelerating field are co-linear. Since the velocity of sub-relativistic particles varies along the acceleration path, proper tapering of the waveguide geometry is required to achieve an extended acceleration region, and, thus a large energy gain. The design of an optimal taper ensuring particle-wave synchronicity and maximum energy gain is pursued through a physics-based approach, and these results are compared, for validation, with the outcomes of a downhill simplex method searching algorithm. Additionally, the application of a simplified 2D model of the accelerating slot waveguide is investigated and profitably used to get qualitative results useful for fast structure optimization. Indeed, this approach can hold significant potential for the development of novel accelerating structures, as it enables a thorough and fast exploration of the design space.

Perspectives in linear accelerator for FLASH VHEE: Study of a compact C-band system.

PURPOSE: In order to translate the FLASH effect in clinical use and to treat deep tumors, Very High Electron Energy irradiations could represent a valid technique. Here, we address the main issues in the design of a VHEE FLASH machine. We present preliminary results for a compact C-band system aiming to reach a high accelerating gradient and high current necessary to deliver a Ultra High Dose Rate with a beam pulse duration of 3µs. METHODS: The proposed system is composed by low energy high current injector linac followed by a high acceleration gradient structure able to reach 60-160 MeV energy range. To obtain the maximum energy, an energy pulse compressor options is considered. CST code was used to define the specifications RF parameters of the linac. To optimize the accelerated current and therefore the delivered dose, beam dynamics simulations was performed using TSTEP and ASTRA codes. RESULTS: The VHEE parameters Linac suitable to satisfy FLASH criteria were simulated. Preliminary results allow to obtain a maximum energy of 160 MeV, with a peak current of 200 mA, which corresponds to a charge of 600 nC. CONCLUSIONS: A promising preliminary design of VHEE linac for FLASH RT has been performed. Supplementary studies are on going to complete the characterization of the machine and to manufacture and test the RF prototypes.

Self-consistent electromagnetic analysis of the microwave-coupling of an electron cyclotron resonance-based charge breeder.

The Electron Cyclotron Resonance (ECR) Charge Breeding (CB) technique consists in transforming the charge state of an input beam from 1+ to n+ to allow post-acceleration. The optimization of an ECR-CB requires a deep investigation of ion dynamics and electron heating, the latter being influenced by the microwave-to-plasma coupling mechanism. In this paper, we report the electromagnetic analysis of the microwave-to-plasma coupling of the Selective Production of Exotic Species charge breeder (SPES-CB) plasma chamber, taking into account the presence of the plasma through its dielectric tensor, performed using a self-consistent approach. In particular, the effect of two different frequencies on the plasma-wave interaction will be shown, in terms of electromagnetic properties such as plasma-absorbed power, giving numerical evidence of the frequency tuning effect.

Self-consistent modeling of beam-plasma interaction in the charge breeding optimization process.

The slowing down and capture by a plasma of externally injected 1+ ions, as a consequence of very frequent elastic Coulomb collisions, is the main mechanism involved in the charge breeding process based on electron cyclotron resonance ion sources. The Istituto Nazionale di Fisica Nucleare ion source group has been undertaking an intense activity on numerical simulations of the beam-plasma interaction, developing a code that has been proven to be very effective in reproducing several experimental results of charge breeding of light and heavy ions. This contribution will present the progress made in the development of the numerical code, focusing the attention on the latest simulations of charge breeding of Rb1+ ions employing a self-consistent plasma target model. The effect of the real plasmoid/halo structure on the capture process will be underlined, as well as the influence of different plasma excitation frequencies.

Experimental characterization of the AISHa ion source.

The Advanced Ion Source for Hadrontherapy (AISHa) has been designed to generate high brightness multiply charged ion beams for hadron therapy applications. AISHa is a compact electron cyclotron resonance ion source whose hybrid magnetic system consists of a permanent Halbach-type hexapole magnet and a set of independently energized superconducting coils. This has allowed us to achieve high performances in a cost effective way. During the commissioning phase, a few criticalities have been observed and fixed in 2018/19; the improvements will be briefly described and the results of the operations with a single 18 GHz generator will be presented. Particular relevance will be given to the production of high intensity beams of oxygen, argon, and carbon, the latter having huge importance for hadron therapy applications. Perspectives for further improvements, including double frequency heating, will also be highlighted.

Postpartum urinary stress incontinence: analysis of the associated risk factors and neurophysiological tests.

AIM: The aim of this paper is to estimate the prevalence of postpartum urinary stress incontinence (USI) three months after vaginal delivery and to analyze the risk factors more frequently correlated with USI. Pelvic floor neurophysiology was performed to assess pudendal nerve damage in symptomatic women. METHODS: A total of 562 women were interviewed and underwent urogynecological evaluation three days after vaginal delivery. They were contacted by telephone 12 weeks later. Chart abstraction was conducted to obtain obstetrical data. Three months after delivery women presenting persistent USI were invited to return for electrophysiological tests. Univariate and logistic regression analyses were performed to reveal any significant association between USI and risk factors. RESULTS: Prevalence of postpartum USI three days after delivery was 15%, decreasing to 10.6% at follow-up three months later. Multivariate analysis of risk factors revealed that persistent USI was significantly associated with: preconception USI (P<0.05), USI developed de novo after delivery (P<0.05), family history of incontinence (P<0.05), chronic cough (P<0.05) and smoking (P<0.05). No obstetric variables were independently connected with incontinence. Neurophysiological tests revealed nerve damage in 36% of the symptomatic puerperae. CONCLUSION: Persistent postpartum incontinence is associated with several maternal and urogynecological risk factors that can help to detect women at risk for early intervention.

Electromagnetic analysis of the plasma chamber of an ECR-based charge breeder.

The optimization of the efficiency of an ECR-based charge breeder is a twofold task: efforts must be paid to maximize the capture of the injected 1+ ions by the confined plasma and to produce high charge states to allow post-acceleration at high energies. Both tasks must be faced by studying in detail the electrons heating dynamics, influenced by the microwave-to-plasma coupling mechanism. Numerical simulations are a powerful tools for obtaining quantitative information about the wave-to-plasma interaction process: this paper presents a numerical study of the microwaves propagation and absorption inside the plasma chamber of the PHOENIX charge breeder, which the selective production of exotic species project, under construction at Legnaro National Laboratories, will adopt as charge breeder. Calculations were carried out with a commercial 3D FEM solver: first, all the resonant frequencies were determined by considering a simplified plasma chamber; then, the realistic geometry was taken into account, including a cold plasma model of increasing complexity. The results gave important information about the power absorption and losses and will allow the improvement of the plasma model to be used in a refined step of calculation reproducing the breeding process itself.

A three-dimensional numerical modelling of the PHOENIX-SPES charge breeder based on the Langevin formalism.

A Charge Breeder (CB) is a crucial device of an ISOL facility, allowing post-acceleration of radioactive ions: it accepts an incoming 1+ beam, then multiplying its charge with a highly charged q+ beam as an output. The overall performances of the facility (intensity and attainable final energy) critically depend on the charge breeder optimization. Experimental results collected along the years confirm that the breeding process is still not fully understood and room for improvements still exists: a new numerical approach has been therefore developed and applied to the description of a (85)Rb(1+) beam capture by the plasma of the 14.5 GHz PHOENIX ECR-based CB, installed at the Laboratoire de Physique Subatomique et de Cosmologie (LPSC), and adopted for the Selective Production of Exotic Species project under construction at Laboratori Nazionali di Legnaro. The results of the numerical simulations, obtained implementing a plasma-target model of increasing accuracy and different values for the plasma potential, will be described along the paper: results very well agree with the theoretical predictions and with the experimental results obtained on the LPSC test bench.

Recent progress in plasma modelling at INFN-LNS.

At Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali del Sud (INFN-LNS), the development of intense ion and proton sources has been supported by a great deal of work on the modelling of microwave generated plasmas for many years. First, a stationary version of the particle-in-cell code was developed for plasma modelling starting from an iterative strategy adopted for the space charge dominated beam transport simulations. Electromagnetic properties of the plasma and full-waves simulations are now affordable for non-homogenous and non-isotropic magnetized plasma via "cold" approximation. The effects of Coulomb collisions on plasma particles dynamics was implemented with the Langevin formalism, instead of simply applying the Spitzer 90° collisions through a Monte Carlo technique. A wide database of different cross sections related to reactions occurring in a hydrogen plasma was implemented. The next step consists of merging such a variety of approaches for retrieving an "as-a-whole" picture of plasma dynamics in ion sources. The preliminary results will be summarized in the paper for a microwave discharge ion source designed for intense and high quality proton beams production, proton source for European Spallation Source project. Even if the realization of a predictive software including the complete processes involved in plasma formation is still rather far, a better comprehension of the source behavior is possible and so the simulations may support the optimization phase.

A new H2 (+) source: Conceptual study and experimental test of an upgraded version of the VIS-Versatile ion source.

The versatile ion source is an off-resonance microwave discharge ion source which produces a slightly overdense plasma at 2.45 GHz of pumping wave frequency extracting more than 60 mA proton beams and 50 mA He(+) beams. DAEδALUS and IsoDAR experiments require high intensities for H2 (+) beams to be accelerated by high power cyclotrons for neutrinos generation. In order to fulfill the new requirements, a new plasma chamber and injection system has been designed and manufactured for increasing the H2 (+) beam intensity. In this paper the studies for the increasing of the H2 (+)/p ratio and for the design of the new plasma chamber and injection system will be shown and discussed together with the experimental tests carried out at Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali del Sud (INFN-LNS) and at Best Cyclotron Systems test-bench in Vancouver, Canada.

The first measurement of plasma density in an ECRIS-like device by means of a frequency-sweep microwave interferometer.

The note presents the first plasma density measurements collected by a novel microwave interferometer in a compact Electron Cyclotron Resonance Ion Sources (ECRIS). The developed K-band (18.5 ÷ 26.5 GHz) microwave interferometry, based on the Frequency-Modulated Continuous-Wave method, has been able to discriminate the plasma signal from the spurious components due to the reflections at the plasma chamber walls, when working in the extreme unfavorable condition λp ≃ Lp ≃ Lc (λp, Lp, and Lc being the probing signal wavelength, the plasma dimension and the plasma chamber length, respectively). The note describes the experimental procedure when probing a high density plasma (ne > 1 ⋅ 1018 cm-3) produced by an ECRIS prototype operating at 3.75 GHz.

Experimental investigation of non-linear wave to plasma interaction in a quasi-flat magnetostatic field.

A characterization of wave-to-plasma interaction in a quasi-flat magnetostatic field at 3.75 GHz has been carried out by using a small-wire movable RF antenna, connected to a spectrum analyzer. The coupling between electromagnetic and electrostatic waves leads to a characteristic spectral emission in low frequency range and around the pumping wave frequency. The most relevant results consist in the broadening of the pumping wave spectrum above critical RF power thresholds and in the generation of sidebands of the pumping frequency, with corresponding components in low frequency domain. The non-linearities are accompanied by the generation of overdense plasmas and intense fluxes of X-rays.

A diary model for monitoring blood pressure in the elderly.

Activity can significantly change blood pressure. Twenty four hour ambulatory blood pressure monitoring (Holter method) was introduced to optimize diagnosis and the changes in blood pressure. It was flanked by the purpose to use diaries to correlate symptoms and pressure changes, pressure changes and psychophysical activity, life style and drugs. The diary model adopted by us for 380 elderly subjects between 65 and 85 years old is divided into four main sections: 1. general activities (8 items); 2. situational variations (7 items); 3. correlation between symptoms and pressure changes; 4. drug treatment and pressure changes. The aim of our study was to assess the compliance of the elderly to keeping a diary. Our results showed that compliance was satisfactory in 352/380 subjects (93%).

Nutritional and behavioral measures in the non-pharmacological treatment of elderly hypertensive subjects.

The antihypertensive treatments have resulted in favorable effects in terms of cardiovascular morbidity and mortality in the elderly, but the therapeutic approaches raise problems linked to the pathophysiological aspects of hypertensives and to the reduced homoeostatic capacity of the senile organism. The antihypertensive treatment in elderly must be aimed at achieving a maximal improvement in the cardiovascular risk profile with possibly minimal side effects. The first step is the non-pharmacological therapy which is a hygienic-behavioral program aimed at changing the patient's life style (physical exercise, reduced salt intake, body weight control, etc.). Non-pharmacological therapy in the elderly patients requires a preliminary evaluating protocol and a close monitoring of the individual responses. The diet, restriction of sodium intake (4-6 g/day), and aerobic physical exercise are important for decrease the development and persistence of hypertension. The non-pharmacological therapy has a low antihypertensive action, however, once established, it should not be abandoned, as its association with pharmacological treatment allows the use of fewer and lower doses of drugs, with a consequent reduction of the risks due to side effects.

Comparison of ambulatory and clinical blood pressures, and their correlation with organic heart damage, in the elderly.

Casual blood pressure (BP) measurements may sometimes indicate the presence of cardiovascular morbidity and mortality, but the correlations between BP values and the subsequent occurrence of such complications are low. This may depend on the known inability of casual BP measurements to reflect accurately the 24-hour mean and overall profile of the BP. In this study, electrocardiography (ECG) of left ventricular muscle mass was related to various measures of BP during circadian ambulatory BP monitoring in 156 hypertensive and non-hypertensive elderly patients. Multiple regression analysis performed to establish the presence of left ventricular hypertrophy (LVH) revealed that the product of ambulatory systolic BP x diastolic BP (p = 0.027) and ambulatory diastolic BP were significant variables. Clinical pressure variables were not significant. Multiple linear regression analysis to establish the degree of LVH in function of the pressure variables generated a model where the variables included are the product of ambulatory systolic BP x diastolic BP (p = 2.7 x 10(-8)), ambulatory systolic BP (p = 7.8 x 10(-6)) and ambulatory diastolic BP (p = 2.4 x 10(-6)). Results obtained agree with the literature and revealed that LVH evaluated using ECG-Romhilt-Estes score was correlated in terms of presence/absence of organ damage and in terms of score to ambulatory monitoring values.

Echocardiographic studies on elderly patients with white coat hypertension to evaluate cardiac organ damages.

This case-control study was aimed at evaluating the distribution of some echocardiographic signs of cardiac organ damages in elderly patients with white coat hypertension (WCH), as compared with a normotensive group of elderly. Correlations between the signs of cardiac organ damages and the clinical and ambulatory blood pressure parameters (obtained by means of a 24-h monitoring) have also been evaluated. The first screening covered 258 elderly subjects of both sexes, aged from 65 to 82 years, with clinical diagnosis of hypertension (systolic and diastolic blood pressures being higher than 160 and 95 mmHg, respectively). Of this group, 116 subjects remained in the final pool, and their echocardiographic parameters were compared with 33 normotensive (N) subjects. Out of the 116 clinically hypertensive patients, 29 (25%) displayed WCH, according to the established criteria. Variance analyses on the ranks followed by Dunn's test revealed no statistically significant differences between the N and WCH groups, while the hypertensive group (H) proved to be significantly different from both the N and the WCH groups. In addition to the descriptive statistics, an analysis of correlations between the pressure variables and the echocardiographic parameters has also been performed by means of a forward-stepwise multiple linear regression method. The models generated by this regression analysis covered only the ambulatory diurnal systolic pressure, and the clinical diastolic pressure in most of the cases of the echocardiographic parameters, taken as independent variables. In all these cases, the standardizecl correlation coefficient of the diurnal systolic pressure was always higher than that of the clinical diastolic pressure, indicating that the echocardiographic parameters depend more strongly on the first than on the second pressure value.

Urinary albumin excretion in elderly patients with white coat hypertension.

The so-called white coat effect occurs in about 42% of elderly patients. This phenomenon leads to several problems in treatment and may also cause renal disease. One of the most frequently controlled parameters is microalbuminuria, an index of renal damage. The present case-control study intended to evaluate the urinary excretion of albumin in elderly patients suffering from white coat hypertension, and comparing their data to those of normotensive subjects. In addition, the study searched for correlations between albuminuria and various clinical and ambulatory blood pressure values. A total of 258 patients were enrolled, but after screening, only 129 were considered; 13 of the latter were further excluded because of problems encountered during ambulatory monitoring of arterial blood pressure. Therefore, 116 hypertensive subjects were included in the study. This pool of hypertensive patients was compared to a normotensive group of 33 subjects. The results have shown the occurrence of white coat effect in 25% of cases, and the microalbuminuria of these patients was statistically not significantly different from that of the normotensive group of patients. The microalbuminuria correlated only with ambulatory systolic blood pressure measured during the day.

[Amlodipine in isolated systolic hypertension in the aged]. / L'amlodipina nell'ipertensione sistolica isolata dell'anziano.

The authors studied the efficacy and safety of a long half-life dihydropyridine calcium-antagonist--amlodipine--in a single daily dose in the treatment of isolated systolic hypertension in the elderly. Ninety-seven subjects, age range 65-85 years, with isolated systolic hypertension were randomized into two groups, similar for age, weight and height, of 47 subjects submitted to active therapy and 50 subjects to placebo, respectively. The study was divided into two phases: in the first one, of three weeks, the first group was administered amlodipine at the dose of 5 mg/day; in the second period, which lasted 9 weeks also in case of systolic pressure normalization, amlodipine at the dose of 10 mg/day was administered. Forty-one subjects of the active drug group and 41 of the control group completed the study. The results were determined as mean +/- standard deviation; statistical analysis was completed by the Student T test. In the amlodipine group, at the end of the third week, a significant decrease in systolic arterial pressure was reported; at the end of the follow-up a further decrease in systolic arterial pressure was observed in the active treatment group as compared to the control group (p < 0.001). The other parameters considered (E.C.G., routine haematochemical tests) did not show significant changes in the two groups during the whole study period. Furthermore, during the follow-up, neither orthostatic hypotension nor reflex tachycardia, events which require particular attention during antihypertensive therapy in the elderly, were observed.(ABSTRACT TRUNCATED AT 250 WORDS)