Increasing Beam Energy Research Articles

Role of Hierarchical Protrusions in Water Repellent Superhydrophobic PTFE Surface Produced by Low Energy Ion Beam Irradiation

The surface wettability of polytetrafluoroethylene (PTFE) was investigated with low energy Ar+ ion beam irradiation varied from 300 eV to 800 eV both at normal and oblique angle of incidence (0°–70°) and at a low irradiation time of few 10 s of seconds. A remarkable change in surface wettability was observed, surface became hydrophobic to superhydrophobic just at 800 eV energy and in 30 s time. A systematic increase in the contact angle was observed with increase in beam energy and irradiation time. For a given ion energy and a threshold irradiation time, the hierarchical protrusions developed that leads to the rolling and bouncing of water droplet even on the horizontal PTFE surface. For the above energy range, the rolling speed was found to be in the range of ~19–31 mm/s. This induced wetting behaviour due to ion irradiation leads to the Cassie-Baxter state as confirmed by the calculation of sliding angle, contact angle hysteresis (CAH) and surface free energy (SE). The CAH values were found to be reduced from 18° for untreated surface (SE ~ 20 mN/m) to 2° for 800 eV, 180 s irradiated surface (SE ~ 0.35 mN/m) at normal incidence.

Isolde V

Isolde V (Isolde five) is a proposal to build two new target stations at the CERN Isolde facility, along with new isotope separators, a high-resolution separator (HRS), and a new beam delivery system.The goals are to fully exploit the investments made in the CERN proton accelerators and the REX/HIE-Isolde post-acceleration linac. In particular this means exploiting the new 2 GeV 4 μA beam from the upgraded PS-Booster, and delivering multiple simultaneous beams to increase the overall isotope production of Isolde by roughly four times.New target stations capable of handling the increased beam energy and intensity from the PS-Booster are expected to deliver considerably higher intensities of short-lived isotopes. The proposal also includes a new HRS to reduce isobaric contamination, and multiple beam-lines with flexible switching to increase the overall operating efficiency of the facility.

Stability modeling of the LHC Nb-Ti Rutherford cables subjected to beam losses

The Large Hadron Collider (LHC) at CERN is being prepared for its full energy exploitation during run III, i.e., an increase of the beam energy beyond the present 6.5 TeV, targeting the maximum discovery potential attainable. This requires an increase of the operating field of the superconducting dipole and quadrupole magnets, which in turn will result in more demanding working conditions due to a reduction of the operating margin while the energy deposited by particle loss will increase. Beam-induced magnet quenches, i.e., the transition to normal conducting state, will become an increasing concern, because they could affect the availability of the LHC. It is hence very important to understand and be able to predict the quench levels of the main LHC magnets for the required values of current and generated magnetic fields. This information will be used to set accurate operating limits of beam loss, with sufficient but not excessive margin, so to achieve maximal beam delivery to the experiments. In this study we used a one-dimensional, multistrand thermal-electric model to analyze the maximum beam losses that can be sustained by the LHC magnets, still remaining superconducting. The heat deposition distribution due to the beam losses is given as an input for the stability analysis. Critical elements of the model are the ability to capture heat and current distribution among strands, and heat transfer to the superfluid helium bath. The computational model has been benchmarked against energy densities reconstructed from beam-induced main dipole quenches during LHC operation at 6.5 TeV. The model was then used to evaluate the stability margin of both main dipole and main quadrupole magnets at different beam energies, up to the expected ultimate operating energy of the LHC, 7.5 TeV. The comparison between the quench levels underlines how the increase of beam energy implies a substantial reduction of magnets stability and will require much stricter setting on the allowable beam losses to avoid resistive transitions during operation.

Editorial

Editorial

Simulated Contrast of Two Dislocations

A three-dimensional Monte Carlo simulation algorithm is used to study the contrast of two dislocations perpendicular to the irradiated surface of an n-doped silicon sample in the electron beam induced current mode. The dislocations are positioned in the irradiation trajectory, and each of both is considered as a cylinder where the minority carrier diffusion length varies abruptly from a low inside dislocations up to a high value outside dislocations. The EBIC contrast was obtained by simulating the random diffusion of carriers generated at point-like sources randomly distributed within the generation volume. Results are analyzed on the basis of change in the generation volume in the bulk of the sample and of carrier trapping process inside dislocations. The EBIC contrast increases with the increase of the electron beam energy. It also increases when the minority diffusion length inside dislocations, or their separating distance decreases.

Event-by-event fluctuations clusterization and entropy production in AA collisions at AGS and SPS energies

Event-by-event (ebe) fluctuations in mean pseudorapidity values of relativistic charged particles in full phase space are studied by analyzing experimental data on [Formula: see text] collisions at 14.5A, 60A and 200A GeV/c and [Formula: see text] collisions at 200A GeV/c. The findings are compared with the prediction of A Multi-Phase Transport (AMPT) model and those obtained from the analysis of correlation free Monte-Carlo events. Fluctuations in mean pseudorapidity distributions are noted to be in excess to that expected from the statistically independent particle emission. The observed dependence of the fluctuation strength measure parameter, [Formula: see text] on the beam energy and number of participating target nucleons indicate that nucleus–nucleus collisions cannot be treated as simple superposition of multiple nucleon–nucleon interactions. Presence of clusters or jet-like phenomena in multihadron final states are searched for on ebe basis by using the concept of Jaynes Shannon entropy. The findings indicate the presence of cluster-like objects in the experimental data with their size and frequency increasing with increasing beam energy. These observations in turn suggest that the clustering or jet-like algorithm adopted in the present study may be used as a tool for triggering different classes of events.

Alan Astbury. 27 November 1934—21 July 2014

Alan Astbury worked in the area of accelerator based subatomic physics. Increasing beam energies, intensities and types of available accelerated beams opened scientific windows to new phenomena throughout his career. Exploiting these new beams required new techniques and the use of the latest technology. Alan was always at the forefront of putting these components together into the experiments needed to confirm or reject the latest theoretical advances or clarify conflicting experimental observations. Following his PhD using the synchrocyclotron at the University of Liverpool and a postdoctoral position at Berkeley, he became a staff member at the Rutherford Appleton Laboratory, where he played a central role in the successive experiments with the Nimrod proton synchrotron, the 26 GeV proton synchrotron at CERN and, perhaps most significantly, with the UA1 experiment at CERN that discovered the W and Z particles. Alan moved to Canada in 1983 and made enormous contributions to Canadian science. He was instrumental in building relationships between Canadian scientists and CERN, DESY and SLAC. As director of the Canadian Institute of Particle Physics and then director of the TRIUMF laboratory, he guided subatomic physics policy and planning for two decades. On the international scene, he was president of the International Union of Pure and Applied Physics.

Simulated contrast of two dislocations -=SUP=-*-=/SUP=-

AbstractA three-dimensional Monte Carlo simulation algorithm is used to study the contrast of two dislocations perpendicular to the irradiated surface of an n -doped silicon sample in the electron beam induced current mode. The dislocations are positioned in the irradiation trajectory, and each of both is considered as a cylinder where the minority carrier diffusion length varies abruptly from a low inside dislocations up to a high value outside dislocations. The EBIC contrast was obtained by simulating the random diffusion of carriers generated at point-like sources randomly distributed within the generation volume. Results are analyzed on the basis of change in the generation volume in the bulk of the sample and of carrier trapping process inside dislocations. The EBIC contrast increases with the increase of the electron beam energy. It also increases when the minority diffusion length inside dislocations, or their separating distance decreases.

Dosimetric Evaluation of Dose calculation algorithms of Monaco Treatment Planning System in the heterogeneities area

Introduction: In radiation therapy, the accuracy of dose calculations by a treatment planning system (TPS) is important to achieve tumor control and to spare normal tissue. Treatment planning system calculations in the heterogeneous situation may present significant inaccuracies. In this study, three different dose calculation algorithms, pencil beam (PB), collapsed cone (CC), and Monte-Carlo (MC), provided by our planning system were compared to assess their impact on the three-dimensional planning of lung region. Materials and Methods: The methodology was based on IAEA TEC-DOC 1583. The phantom resembling the human thorax are used and all tests were planned on three- dimensional treatment planning systems (TPSs) and irradiated with photon beams of 6, and 18 MV X-ray energies. The doses in specific points were measured with an ionization chamber. The differences between the measured and calculated doses were reported. This study was tested using different algorithms/inhomogeneity correction methods implemented in Monaco treatment planning system. Results: The measurements were conducted for all test case datasets for two photon beam energies and calculation algorithms. The deviation between the measured and calculated values for all test cases made with advanced algorithms (MC and CC) were within the agreement criteria, while the larger deviations were observed for PB algorithm. Subsequently, there were discovered dose differences greater than 20% for some simple algorithms and high energy X-ray beams. The number of measurements with results outside the agreement criteria increased with the increase of the beam energy and decreased with TPS calculation algorithm sophistication. Also, a few errors in the basic dosimetry data in TPS were detected and corrected. Conclusion: Differences were found when comparing the calculation algorithms. The PB algorithm actually overestimated the dose compared with those calculated by the CC and MC algorithms. The MC algorithm showed better accuracy than the other algorithms. Therefore advanced dose calculation algorithms are suitable and should be used in clinical practice

Evaluation of organs at risk dose in the left breast IOERT procedures whit and without shielding disc using monte carlo simulation

Introduction: One of the treatment choices in breast cancer is Intra operative electron beam radiation therapy (IOERT). Due to high dose delivery in this procedure, shielding disk is used to protect organs at risk (OARs). In this study, we evaluate the OARs dose in the breast IOERT using Monte Carlo simulation with and without shielding disk in RANDO phantom. Material and Methods: Simulation of dedicated IOERT linear accelerator (LIAC) head with 5cm diameter applicator was performed using BEAMnrc Monte Carlo simulation cod. Three phase-space files for each nominal electron beam energies (6,8,10,12 MeV) produced in the end of the applicator, after 2 cm tissue in the end of applicator. The last phase-space was created after disk. These phase- space were used in DOSXYZnrc for irradiation of RANDO phantom. Both lungs and heart were considered as OARs in the IOERT of the left breast irradiation. For each energy, the 3ddose files, as an output of DOSXYZnrc and contoured organs in the RANDO phantom imported to CERR software. 12Gy was considered as a normalized value in the target. Then dose-volume- histogram (DVH) data were extracted for analysis. Results: The mean and maximum dose for each OAR in all energies with and without disk and with consideration of 2 cm tissue as a target were extracted from DVH data. For all nominal energies, the right lung dose was zero. The maximum and mean dose range in the left lung without disk were 11.5-13.9 and 0.15-0.5 Gy, respectively. These values for heart were 0-2.9 and 0-0.16Gy. The mean dose of heart and the left lung were un-remarkable with applying 2cm tissue and disk. Conclusion: With the increase of the electron beam energy in the IOERT, an increase of OARs dose was seen with and without shielding disk application. On the other hand, application of shielding disk in breast IOERT reduces OARs dose significantly

Nuclear dynamics in multinucleon transfer reactions near Coulomb barrier energies

The mechanism of multinucleon transfer reactions has been investigated within the dinuclear system model, in which the sequential nucleon transfer is described by solving a set of microscopically derived master equations. The transfer dynamics in the reaction of $${^{136}}{\mathrm{Xe}}+{^{208}}{\mathrm{Pb}}$$ near Coulomb barrier energies is thoroughly analyzed. It is found that the total kinetic energies of primary fragments are dissipated from the relative motion energy of two touching nuclei and exhibit a symmetric distribution along the fragment mass. The angular distribution of the projectile-like fragments moves forward with increasing beam energy. However, the target-like fragments exhibit an opposite trend. The shell effect is pronounced due to the fragment yields in multinucleon transfer reactions.

Production of 15O for Medical Applications via the 16O(γ,n)15O Reaction.

15O (half-life, 122 s) is a useful radionuclide for PET applications. Current production of 15O typically makes use of the 14N(d,n)15O, 15N(p,n)15O, or 16O(p,pn)15O reactions using an accelerator. A novel approach for the production of 15O is via the 16O(γ,n)15O reaction using an electron linear accelerator. Photonuclear reactions using an electron linear accelerator may allow for feasible and economical production of 15O compared with the current methods. Methods: In this work, experiments using a repurposed Clinac were conducted using oxygen-containing alumina as a target material to study the production rate of 15O. Additional studies were conducted using a water target cell. Simulations using Geant4 were conducted to predict the activity and power dissipation in the target. Results: Bremsstrahlung radiation from the electron beam, and consequently 15O production via photonuclear reactions, is enhanced when a high-Z material, tungsten, is placed in front of the target. The alumina irradiations provided preliminary data to optimize the beam parameters and target configuration. The optimal thickness of tungsten was 1.4 mm for both the simulated and the measured studies of alumina. Simulations of irradiated water targets showed that tungsten thicker than 1.4 mm resulted in fewer photons available to activate the water; thus, a higher current was required to achieve a fixed dose. Alternatively, for a constant tungsten thickness, more power was deposited in the target with increasing beam energy, requiring a lower current to achieve a fixed dose. Actual irradiations of a water target yielded a quantity of 15O in the water that was consistent with expectations based on irradiations of alumina. Conclusion: Several parameters should be considered regarding the photonuclear production of 15O for an average patient dose of 1,850 MBq (50 mCi) in 10 mL. This work illustrates a variety of machine parameters capable of achieving a reasonable patient dose. Our simulations show that the power deposited in the target for these parameters is less than that in commercially operated cyclotron targets for the production of 18F. Thus, this work demonstrates that the photonuclear production of 15O may be a new production path for this useful radionuclide.

L-shell X-ray production cross sections in metal oxide thin films due to 12C, 16O and 28Si ion beams at MeV SIMS energies

Successful co-implementation of different heavy ion beam nuclear analytical techniques such as heavy ion PIXE, ERDA, MeV SIMS and RBS hinges on the availability of accurate databases of fundamental ion beam-matter interaction parameters. We report on measurements carried out to determine L-shell X-ray production cross sections in 101Ru and 181Ta due to 12C, 16O and 28Si projectile ions in the 0.2 MeV/u–1.0 MeV/u energy range. Experimental data is compared to calculations by one of the most widely implemented X-ray ionisation theories in PIXE analyses – the ECPSSR theory in its modified United Atom (UA) version. Results show fairly good agreement between experiment and theory for the 181Ta target atoms, with the level of agreement improving as the Zion/Ztarget ratio decreases and as beam energy increases. For 101Ru target atoms theoretical predictions tend to underestimate experimental data and the discrepancies increase with projectile mass and decreasing energy. The contribution of projectile electron capture (EC) to the measured X-ray production cross sections is also considered in the data analysis and discussion.

Photon production from Pb + Pb collisions at sNN=5.02 TeV at the CERN Large Hadron Collider and at sNN=39 TeV at the proposed Future Circular Collider facility

We calculate the production of prompt and thermal photons from Pb+Pb collisions at 5.02A TeV at the Large Hadron Collider (LHC) and at 39A TeV at the proposed Future Circular Collider (FCC) facility. The photon spectra and anisotropic flow at these energies are compared with the results obtained from 2.76A TeV Pb+Pb collisions at the LHC for three different centrality bins. The prompt photons originating from initial hard scatterings are found to increase by a factor of 1.5 to 2 at 5.02A TeV in the $p_T$ region 2 to 15 GeV and the enhancement is found to be about 5 to 15 times at FCC energy compared to 2.76A TeV in the same $p_T$ region. The evolution of the Quark-Gluon Plasma (QGP) formed in Pb+Pb collisions at LHC and FCC energies are studied using a hydrodynamical model and the $p_T$ spectra and elliptic flow of thermal photons are calculated using state-of-the-art photon rates. The relative enhancement in the production of thermal photons is found to be more compared to prompt photons at FCC than at the LHC energies. Although the production of direct (prompt+thermal) photons is found to enhance significantly with increase in beam energy, the photon elliptic flow increases only marginally and does not show strong sensitivity to the collision energy.

Beam energy dependence of the squeeze-out effect on the directed and elliptic flow in Au + Au collisions in the high baryon density region

We present a detailed analysis of the beam energy dependence of the mechanisms for the generation of directed and elliptic flows in Au+Au collisions focusing on the role of hadronic rescattering and spectator shadowing within a microscopic transport model JAM with different equation of state. A systematic study of the beam energy dependence is performed for Au+Au collisions at $\sqrt{s_{NN}} =2.3 - 62.4$ GeV. The transition of the dynamical origin of the directed flow is observed. We find that the initial Glauber type nucleon-nucleon collisions generate negative $v_1$ for nucleons at midrapidity due to the presence of spectator matter, and this negative nucleon $v_1$ is turned to be positive by the meson-baryon interactions at the beam energy region of $\sqrt{s_{NN}} < 30$ GeV. In contrast, above 30 GeV there is no spectator shadowing at midrapidity, and initial nucleon-nucleon collisions do not generate directed flow, but subsequent rescatterings among produced particles generate negative $v_1$ for nucleons. It is demonstrated that negative pion-directed flows are mostly generated by the interaction with the spectator matter. It is also shown that the squeeze-out effect is largely suppressed in the case of softening, which leads to the enhancement of elliptic flow around $\sqrt{s_{NN}}=5-7$ GeV. The elliptic flow at midrapidity above 10 GeV is not influenced by the squeeze-out due to spectator matter, while its effect is seen at the forward rapidity range of $y/y_\mathrm{c.m.}>0.5$, which decreases as beam energy increases.

Effects of the in-medium nucleon-nucleon cross section on collective flow and nuclear stopping in heavy-ion collisions in the Fermi-energy domain

With the newly updated version of the ultrarelativistic quantum molecular dynamics (UrQMD) model, a systematic investigation of the effects of in-medium nucleon-nucleon ($\mathit{NN}$) elastic cross section on the collective flow and the stopping observables in $^{197}\mathrm{Au}+^{197}\mathrm{Au}$ collisions at beam energies from 40 to 150 MeV/nucleon is performed. Simulations with the medium correction factors $\mathcal{F}={\ensuremath{\sigma}}_{NN}^{\mathrm{in}\text{\ensuremath{-}}\mathrm{medium}}/{\ensuremath{\sigma}}_{NN}^{\mathrm{free}}=0.2,0.3,0.5$ and the one obtained with the FU3FP1 parametrization which depends on both the density and the momentum are compared to the FOPI and INDRA experimental data. It is found that, to best fit the experimental data of the slope of the directed flow and the elliptic flow at midrapidity as well as the nuclear stopping, the correction factors of $\mathcal{F}=0.2$ and 0.5 are required for reactions at beam energies of 40 and 150 MeV/nucleon, respectively. Whereas calculations with the FU3FP1 parametrization can simultaneously reproduce these experimental data reasonably well. And, the observed increasing nuclear stopping with increasing beam energy in experimental data can also be reproduced by using the FU3FP1 parametrization, whereas the calculated stopping power in Au + Au collisions with beam energies from 40 to $150\phantom{\rule{0.28em}{0ex}}\mathrm{MeV}/\mathrm{nucleon}$ almost remains constant when taking $\mathcal{F}$ equal to a fixed value.

Coulomb Interaction Effects on Pion Production in Au+Au Collisions at Relativistic Energies

Coulomb effects on charged pion transverse momentum spectra measured in Au+Au collisions at RHIC-BES energies are investigated. From these spectra the π-/π+ ratios as a function of transverse momentum are obtained and used to extract the “Coulomb kick”, pc (a momentum change due to the Coulomb interaction), and initial pion ratio for three different collision energies and various centrality classes. The Coulomb kick shows a decrease with the increase of beam energy and a clear centrality dependence, with larger values for the most central collisions. The results are connected with the kinetic freeze-out dynamics.

Measured and Monte Carlo simulated surface dose reduction for superficial X-rays incident on tissue with underlying air or bone.

Measurement of surface dose reduction effects for superficial x-rays incident on tissue with underlying air or bone and comparison with Monte Carlo simulations of such effects. Further to investigate the correlation between surface dose reduction and changes in Compton backscatter spectra with tissue-bone separation. An Advanced Markus chamber with entrance window facing downstream on the surface of a solid water phantom was used to investigate changes in surface dose with an underlying air or bone interface located at various depths below the surface. Chamber readings were obtained for interface depths ranging from 1 to 100 mm using the 50 kV, 100 kV and 150 kV beams of an Xstrahl 150 x-ray unit, with field diameters (ϕ) = 2.5 cm and 5 cm. For each beam quality and field size the dose correction factor, DCF(t), namely the ratio of measured dose (t) to dose (t = 100 mm) was determined. Monte Carlo simulations of DCF(t) for air and bone interfaces in tissue are used to validate corresponding measured data. For a given beam and field size, the difference between simulated spectra with an air or bone interface at t = 3 mm was used to determine the Compton backscatter from bone at the surface. For air, DCF(t < 40 mm) is less than unity and for a given t DCF(t) decreases as beam energy increases from 50 kV to 150 kV. Conversely for bone DCF(t < 40 mm) increases for a given t with increasing beam energy. In particular for t = 1 mm, ϕ = 5 cm, DCF for air(bone) are 0.90(0.92) and 0.86(0.96) for 50 kV and 150 kV, respectively. For the same tube potentials corresponding factors, ϕ = 2.5 cm, for air(bone) are 0.94(0.96) and 0.92(0.99). Calculated DCF(t) based on Monte Carlo simulations are consistent with experimental observations to within 2%. Monte Carlo simulations of x-ray spectra demonstrate the presence of Compton backscatter from underlying bone in tissue. With bone at 3 mm depth calculated backscatter spectra at the tissue surface suggest that surface dose is influenced by the proximity of bone and that this effect depends on beam quality. This work demonstrates the feasibility of using an Advanced Markus chamber with entrance window facing downstream to investigate surface dose reduction with underlying air or bone in tissue. As the field size decreases and beam quality increases surface dose with underlying bone tends to full backscatter values even though tissue thicknesses are below those normally associated with full backscatter. Conversely with underlying bone close to the surface dose will increasingly fall below full backscatter values as the beam energy is reduced and field size is increased.

Monaco and film dosimetry of 3D CRT, IMRT and VMAT cases in a realistic pelvic prosthetic phantom

The dosimetry of patients with metallic hip implants during irradiation of pelvic lesions is challenging due to dose distortions caused by implants. This work presents a dosimetric comparison of various multi-field photon-beam dose distributions in the presence of unilateral hip titanium prosthesis (UHTiP) embedded in a unique pelvic phantom made out of water-equivalent nylon slices. The impact of the UHTiP on the accuracy of dose calculations from a Monaco TPS (treatment planning system) using the X-ray voxel Monte Carlo (XVMC) algorithm was benchmarked against measured dose data using Gafchromic EBT3 film. Multi-field beam arrangements including a 4-field box, 5-field 3DCRT (three-dimensional conformal radiation therapy), 6-field IMRT (intensity modulated radiation therapy) and a single-arc VMAT (volumetric modulated arc therapy) plan were set up for 6MV and 15MV beams. These plans were generated for the pelvic phantom that contains the prosthesis with film inserted. Compared to Monaco TPS dose calculations, film measurements showed enhanced dose in the prosthesis which was not predicted by Monaco due to its limitation in relative density assignment. The enhanced prosthesis dose increased with increase in beam energy and decreased with the complexity of the treatment plans, with VMAT giving the least escalated dose. The dose increased between 5% and 19% for 6MV and between 6% and 21% for 15MV. A gamma index analysis showed that 70–92% of dose points (excluding the prosthesis) were within 3% discrepancy. Increasing the number of treatment fields increases target dose coverage and improves the agreement between film and Monaco. When the relative electron density (RED) in the prosthesis was varied between 3.72 and 15 the dose discrepancy between film and Monaco increased from 30% to 57% for 6MV and from 30% to 50% for 15MV. The study indicates that beam weights for fields that pass through the prosthesis should be minimised and its RED must be correct for accurate dose calculation on Monaco.

Main improvements of LHC Cryogenics Operation during Run 2 (2015-2018)

After the successful Run 1 (2010-2012), the LHC entered its first Long Shutdown period (LS1, 2013-2014). During LS1 the LHC cryogenic system went under a complete maintenance and consolidation program. The LHC resumed operation in 2015 with an increased beam energy from 4 TeV to 6.5 TeV. Prior to the new physics Run 2 (2015-2018), the LHC was progressively cooled down from ambient to the 1.9 K operation temperature. The LHC has resumed operation with beams in April 2015. Operational margins on the cryogenic capacity were reduced compared to Run 1, mainly due to the observed higher than expected electron-cloud heat load coming from increased beam energy and intensity. Maintaining and improving the cryogenic availability level required the implementation of a series of actions in order to deal with the observed heat loads. This paper describes the results from the process optimization and update of the control system, thus allowing the adjustment of the non-isothermal heat load at 4.5 – 20 K and the optimized dynamic behaviour of the cryogenic system versus the electron-cloud thermal load. Effects from the new regulation settings applied for operation on the electrical distribution feed-boxes and inner triplets will be discussed. The efficiency of the preventive and corrective maintenance, as well as the benefits and issues of the present cryogenic system configuration for Run 2 operational scenario will be described. Finally, the overall availability results and helium management of the LHC cryogenic system during the 2015-2016 operational period will be presented.