Numerical studies of a plasma accelerator driven free electron laser

The Free Electron Laser (FEL) is a unique source of tunable, coherent light, that is particularly important towards and into the x-ray region of the spectrum. After the achievement of FEL lasing that is based on conventional acceleration utilizing radiofrequency cavities, a significant challenge is the creation of an compact FEL working with an electron bunching accelerated via plasma-based accelerators. However, electron beams produced by some plasma accelerators with large normalized emittance, significant levels of energy spread and energy chirp are a major challenge towards driving FELs. Novel plasma-based acceleration and injection methods, such as beam driven under dense Plasma photocathode Wake-Field Acceleration (PWFA), promises electron beams with ultra-low normalized emittance, high peak currents and low energy spreads. The plasma photocathode injection method is an advanced plasma based electron injector which releases electrons directly inside a PWFA by selectively laser-ionizing a neutral background gas. A 250 MeV electron beam from a PWFA with a fs-scale duration, mmmrad normalized emittance and with a natural negative energy chirp is investigated. This thesis uses simulations to explore the capability of a plasma photocathode to drive an FEL and to investigate the effects of the electron beam energy chirp on lasing. It is shown that removing the energy chirp is a key to enable the high quality beams to achieve FEL lasing. The beam is first used as delivered – with relatively high chirp and then with the chirp removed. The VSim code is used to model the plasma accelerator, and the Puffin code for the FEL process. A dynamically evolving current profile, due to energy chirp changing the electron pulse current profile, induces ballistic bunching at moderate energies. This bunching can generate significant coherent radiation via the process of Coherent Spontaneous Emission (CSE). While this CSE is seen to drive some FEL-induced electron bunching at the radiation wavelength, the dynamic evolution of the energy chirped pulse dampens out any high-gain FEL bunching interaction. When the beam energy chirp was removed numerically, the FEL was shown to lase via the high-gain FEL interaction and exponential gain was demonstrated. Therefore, if the energy chirp of the beam can be reduced experimentally, and on-going research is suggesting this is possible, this opens the prospect of a future PWFA FEL operating in the high-gain regime.The Free Electron Laser (FEL) is a unique source of tunable, coherent light, that is particularly important towards and into the x-ray region of the spectrum. After the achievement of FEL lasing that is based on conventional acceleration utilizing radiofrequency cavities, a significant challenge is the creation of an compact FEL working with an electron bunching accelerated via plasma-based accelerators. However, electron beams produced by some plasma accelerators with large normalized emittance, significant levels of energy spread and energy chirp are a major challenge towards driving FELs. Novel plasma-based acceleration and injection methods, such as beam driven under dense Plasma photocathode Wake-Field Acceleration (PWFA), promises electron beams with ultra-low normalized emittance, high peak currents and low energy spreads. The plasma photocathode injection method is an advanced plasma based electron injector which releases electrons directly inside a PWFA by selectively laser-ionizing a neutral background gas. A 250 MeV electron beam from a PWFA with a fs-scale duration, mmmrad normalized emittance and with a natural negative energy chirp is investigated. This thesis uses simulations to explore the capability of a plasma photocathode to drive an FEL and to investigate the effects of the electron beam energy chirp on lasing. It is shown that removing the energy chirp is a key to enable the high quality beams to achieve FEL lasing. The beam is first used as delivered – with relatively high chirp and then with the chirp removed. The VSim code is used to model the plasma accelerator, and the Puffin code for the FEL process. A dynamically evolving current profile, due to energy chirp changing the electron pulse current profile, induces ballistic bunching at moderate energies. This bunching can generate significant coherent radiation via the process of Coherent Spontaneous Emission (CSE). While this CSE is seen to drive some FEL-induced electron bunching at the radiation wavelength, the dynamic evolution of the energy chirped pulse dampens out any high-gain FEL bunching interaction. When the beam energy chirp was removed numerically, the FEL was shown to lase via the high-gain FEL interaction and exponential gain was demonstrated. Therefore, if the energy chirp of the beam can be reduced experimentally, and on-going research is suggesting this is possible, this opens the prospect of a future PWFA FEL operating in the high-gain regime

Modelling a laser plasma accelerator driven free electron laser

Free-electron lasers (FEL) are the brightest, coherent sources of short wavelength radiation from the VUV into the x-ray. There is much research interest in reducing the cost and the size of FELs by utilising new accelerator techniques. Laser-plasma accelerator (LPA) are a promising accelerator for next generation compact FEL light sources with many potential advantages due to the high acceleration gradient and large peak currents they offer. The electron beams of a LPA typically have a smaller transverse emittance, a large energy spread and tend to be of shorter duration and higher current than conventional Radio Frequency (RF) accelerators. In this paper, a FEL driven by an electron beam from a typical LPA was simulated using the 3D FEL simulation code Puffin. It is shown that lowering the homogenous electron beam energy spread increases the radiation energy output in a short undulator and , as become less than the FEL, or Pierce parameter ($\rho$), then the peak radiation energy increases and the saturation length reduces significantly as expected

Plasma wakefield accelerator driven coherent spontaneous emission from an energy chirped electron pulse

Plasma accelerators (Esaryet al2009Rev. Mod. Phys.811229) are a potentially important source of highenergy, low emittance electron beamswith high peak currents generated within a relatively short distance. As such, they may have an important application in the driving of coherent light sources such as the Free Electron Laser (FEL) which operate into the x-ray region (McNeil and Thompson 2010 Nat. Photon.4814–21). While novel plasma photocathodes (Hidding et al 2012 Phys. Rev. Lett. 108035001) may offer orders of magnitude improvement to the normalized emittance and brightness of electron beams compared to Radio Frequency-driven accelerators, a substantial challenge is the energy spread and chirp of beams, which can make FEL operation impossible. In this paper it is shown that such an energy-chirped, ultrahigh brightness electron beam, with dynamically evolving current profile due to ballistic bunching at moderate energies, can generate significant coherent radiation output via the process of Coherent Spontaneous Emission (CSE) (Campbell and McNeil 2012 Proc. FEL2012 (Nara, Japan)).While this CSE is seen to cause some FEL-induced electron bunching at the radiation wavelength, the dynamic evolution of the energy chirped pulse dampens out any high-gain FEL interaction. This work may offer the prospect of a future plasma driven FEL operating in the high-gain Self Amplified CSE mode

Management of hospitalized drug sensitive pulmonary tuberculosis patients during the Hajj mass gathering: A cross sectional study

Background To document the management of drug-sensitive TB patients during the Hajj and assess compliance with the Saudi TB management guidelines. Method The study was conducted in hospitals in Makkah during the 2016 and 2017 Hajj seasons. Structured questionnaire was used to collect data on relevant indices on TB management and a scoring system was developed to assess compliance with guidelines. Results Data was collected from 31 TB cases, 65.4% (17/26) were Saudi residents. Sputum culture was the only diagnostic test applied in 67.7% (21/31) of patients. Most (96.8%, 30/31) confirmed TB cases were isolated, but only 12.9% (4/28) were tested for HIV and merely 37% (10/27) received the recommended four 1st-line anti-TB drugs. Guideline compliance scores were highest for infection prevention and control and surveillance (9.6/10) and identifying TB suspects (7.2/10). The least scores were obtained for treating TB (5.0/10) and diagnosing TB (3.0/10). Conclusions Healthcare providers training and supervision are paramount to improve their knowledge and skill and ensure their compliance with existing TB management guidelines. However, there may be a need for the introduction of an international policy/guideline for TB control and management during mass gatherings such as the Hajj to guide providers’ choices and facilitate monitoring

Tuberculosis Trends in Saudis and Non-Saudis in the Kingdom of Saudi Arabia – A 10 Year Retrospective Study (2000–2009)

Tuberculosis (TB) remains a public health problem in the Kingdom of Saudi Arabia (KSA), which has a very large labour force from high TB endemic countries. Understanding the epidemiological and clinical features of the TB problem, and the TB burden in the immigrant workforce, is necessary for improved planning and implementation of TB services and prevention measures

Solvability of second order linear differential equations in the sequence space n(ϕ) n(ϕ)n(\phi)

Abstract We apply the concept of measure of noncompactness to study the existence of solution of second order differential equations with initial conditions in the sequence space n(ϕ) $n(\phi)$

Effective adsorption of metals on porphyrins: Experiments and advanced isotherms modeling

In this article, the investigation of the adsorption process of six metal compounds (aluminum chloride, aluminum sulfate, iron chloride, iron sulfate, indium chloride and indium sulfate) on the promising macromolecule named porphyrin was performed to prove new insights about the metals-porphyrin complexes. The experimental adsorption data of the six complexation systems were controlled at four reaction temperatures using the well-known microbalance apparatus (QCM). In fact, the experimental outcomes and the physical modeling treatment indicated that the complexation process of aluminium and iron should be analyzed via the mono-layer adsorption model whereas; the interaction between the two indium compounds and the porphyrin was described via the double-layer model. Actually, the physicochemical description showed that the three metals were adsorbed via a multi-docking mechanism. The fitted values of the paramount parameter density of the adsorbent sites showed the endothermic character of the studied processes. Thus, some porphyrin sites were activated only at high temperature. The down trend of the iron isotherms was explained through the van der Waals parameters which describe the lateral interactions influences. The calculation of the adsorption energies which describe the interactions between the adsorbates and the adsorbent showed that chemical bonds were carried out between the aluminum and the porphyrin. The thermodynamic study, through the two thermodynamic functions (the configurational entropy and the free enthalpy), showed that the disorder of the six processes is maximum at the level of the energetic parameters and that the six complexation mechanisms advanced spontaneously towards saturation. For the iron, the behavior of the enthalpy indicated that the lateral interactions between the adsorbates disfavored the adsorption of iron chloride and iron sulfate at high concentration. The double-layer process of the indium was confirmed by the trends of the free enthalpies which showed two stability states for the two indium compounds

Undiagnosed Active Pulmonary Tuberculosis among Pilgrims during the 2015 Hajj Mass Gathering: A Prospective Cross-sectional Study

Mass gatherings pose a risk for tuberculosis (TB) transmission and reactivation of latent TB infection. The annual Hajj pilgrimage attracts 2 million pilgrims many from high TB-endemic countries. We evaluated the burden of undiagnosed active pulmonary TB in pilgrims attending the 2015 Hajj mass gathering. We conducted a prospective cross-sectional study in Mecca, Kingdom of Saudi Arabia, for nonhospitalized adult pilgrims from five high TB-endemic countries. Enrollment criteria were the presence of a cough and the ability to produce a sputum sample. Sputum samples were processed using the Xpert MTB-RIF assay. Data were analyzed for drug-resistant TB, risk factors, and comorbidities by the country of origin. Of 1,164 consenting pilgrims enrolled from five countries: Afghanistan (316), Bangladesh (222), Nigeria (176), Pakistan (302), and South Africa (148), laboratory results were available for 1,063 (91.3%). The mean age of pilgrims was 54.5 (range = 18–94 years) with a male to female ratio of 2.6:1; 27.7% had an underlying comorbidity, with hypertension and diabetes being the most common, 20% were smokers, and 2.8% gave a history of previous TB treatment. Fifteen pilgrims (1.4%) had active previously undiagnosed drug-sensitive pulmonary TB (Afghanistan [12; 80%], Pakistan [2; 13.3%], and Nigeria [1; 6.7%]). No multidrug-resistant TB cases were detected. Pilgrims from high TB-endemic Asian and African countries with undiagnosed active pulmonary TB pose a risk to other pilgrims from over 180 countries. Further studies are required to define the scale of the TB problem during the Hajj mass gathering and the development of proactive screening, treatment and prevention guidelines