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The LHC beam luminosity monitor is based on the following principle. The neutrals that originate in LHC at every PP interaction create showers in the absorbers placed in front of the cryogenic separation dipoles. The shower energy, as it can be measured by suitable detectors in the absorbers is proportional to the number of neutral particles and, therefore, to the luminosity. This principle lends itself to a luminosity measurement on a bunch-by-bunch basis. However, detector and front-end electronics must comply with extremely stringent requirements. To make the bunch-by-bunch measurement feasible, their speed of operation must match the 40 MHz bunch repetition rate of LHC. Besides, in the actual operation the detector must stand extremely high radiation doses. The front-end electronics, to survive, must be located at some distance from the region of high radiation field, which means that a properly terminated, low-noise, cable connection is needed between detector and front-end electronics. After briefly reviewing the solutions that have been adopted for the detector and the front-end electronics and the results that have been obtained so far in tests on the beam, the latest version of the instrument in describe in detail. It will be shown how a clever detector design, a suitable front-end conception based on the use of a "cold resistance" cable termination and a careful low-noise design, along with the use of an effective deconvolution algorithm, make the luminosity measurement possible on a bunch-by-bunch basis at the LHC bunch repetition rates.

This paper discusses the criteria that have been adopted to optimize the signal processing in a shower detector to be employed as LHC beam luminosity monitor. The original aspect ofthis instrument is its ablility to operate on a bunch-by-bunch basis. This means that it must perform accurate charge measurements at a repetition rate of 40 MHz. The detector must withstand an integrated dose of 100 Grad, that is, two to three orders of magnitude beyond those expected in the experiments. To meet the above requirements, an ionization chamber consisting of several gaps of thickness 0.5 mm, filled with a gas that is expected to be radiation resistant, has been designed. Crucial in the development of the system is the signal processing, as the electronic noise may set the dominant limitation to the accuracy of the measurement. This is related to two aspects. One is the short time available for the charge measurement. The second one is the presence of a few meter cable between the detector and the preamplifier, as this must be located out of the region of highest radiation field. Therefore the optimization of the signal-to-noise ratio requires that the best configuration of the chamber gaps be determined under the constraint of the presence of a cable of non-negligible length between detector and preamplifier. The remote placement of the amplifying electronics will require that the front-end electronics be radiation hard although to a lesser extent than the detector.

The front IR quadrupole absorbers (TAS) and the IR neutral particle absorbers (TAN) in the high luminosity insertions of the Large Hadron Collider (LHC) each absorb approximately 1.8 TeV of forward collision products on average per pp interaction (~;235W at design luminosity 1034cm-2s-1). This secondary particle flux can be exploited to provide a useful storage ring operations tool for optimization of luminosity. A novel segmented, multi-gap, pressurized gas ionization chambers is being developed for sampling the energy deposited near the maxima of the hadronic/ electromagnetic showers in these absorbers. The ionization chamber must be capable of resolving individual bunch crossings at 40MHz. The ionization chamber is segmented into quadrants; each quadrant consists of sixty (40x40)mm2 Cu plates 1.0mm thick, with 0.5mm gaps. The 0.5mm gap width has been chosen so that the time for the ionization electrons to drift across the gap, is short enough to produce at the output of the shaping amplifier, a signal that returns to the base line is less than the 25ns bunch spacing of the LHC. From noise considerations in the presence of a cable the stack of plates are connected electrically 10 in parallel, 6 in series to achieve an equivalent detector capacitance Cd~;50pF. This type connection forms an electrode inductive Le and electrode capacitive Ce network that must be optimized to transfer charge from the chamber to the sensing amplifier. This paper describes the design of the collection electrodes optimized for 40 MHz operation.

Synchrotron radiation induced photodesorption in particle accelerators may lead to pressure rise and to beam-gas scattering losses, finally affecting the beam lifetime. We discuss the beam tube vacuum in the low field Stage 1 Very Large Hadron Collider VLHC. Since VLHC Stage 1 has a room temperature beam tube, a non-evaporable getter (NEG St101 strip) pumping system located inside a pumping antechamber, supplemented by lumped ion pumps for pumping methane is considered. A possible beam conditioning scenario is presented for reaching design intensity. The most important results are summarized in this paper. More detailed reports of the calculations will be presented at the PAC2001 Conference, Chicago, IL to be held in June 2001, and at the Snowmass Conference, CO, to be held on July 2001.

The front IR quadrupole absorbers (TAS) and the IR neutral particle absorbers (TAN) in the high luminosity insertions of the LHC each absorb approximately 1.8TeV of forward collision products on average per pp interaction (~;;235W at design luminosity 1034cm-2s-1). This secondary particle flux can be exploited to provide a useful storage ring operations tool for optimization of luminosity. Novel segmented, multi-gap, pressurized gas ionization chambers are proposed for sampling the energy deposited near the maxima of the hadronic/ electromagnetic showers in these absorbers. The system design choices have been strongly influenced by optimization of signal to noise ratio and by the very high radiation environment. The ionization chambers are instrumented with state of the art low noise, fast, pulse shaping electronics capable of resolving individual bunch crossings at 40 MHz. Data on each bunch are separately accumulated over multiple bunch crossings until the desired statistical accuracy is obtained. At design luminosity approximately 2x103 bunch crossings suffice for a 1percent luminosity measurement.

The Large Hadron Collider forward and the Relativistic Heavy Ion Collider forward experiments measured forward particles produced in high-energy hadron collisions at the LHC and RHIC. Using compact calorimeters neutral particles produced in pseudorapidities η >8.4 and η >6.0 are observed by the respective experiments. Because the collision energies ranging from 0.51 TeV to 13 TeV correspond to the cosmic-ray equivalent energies of 1014 to 1017 eV, the measurements are important to understand the hadronic interaction relevant to extensive air shower measurements. This paper reviews recent results of LHCf and initial performance of RHICf that took data in the 2017 RHIC operation.

The Large Hadron Collider is intensively used to test hadronic interaction models used in cosmic-ray physics because its maximum (designed) collision energy √s = 14 TeV corresponds to the interaction of a 1017 eV cosmic-ray proton hitting the atmosphere. In this paper various types of forward experiments at the LHC, where the particles relevant to the air shower development are observed, are reviewed. Recent results of a dedicated experiment for precise forward measurement, the LHC forward, are discussed in detail. A future possibility at the LHC, light ion collisions, is also discussed.

The LHCf experiment, optimized for the study of forward physics at LHC, completes its main physics program in this year 2015, with the proton-proton collisions at the energy of 13 TeV. LHCf gives important results on the study of neutral particles at extreme pseudo-rapidity, both for proton-proton and for proton-ion interactions. These results are an important reference for tuning the models of the hadronic interaction currently used for the simulation of the atmospheric showers induced by very high energy cosmic rays. The results of this analysis and the future perspective are presented in this paper.

A novel segmented multigap pressurized gas ionization chamber is being developed for optimization of the luminosity of the Large Hadron Collider (LHC). The ionization chambers are to be installed in the front quadrupole and 0[degrees] neutral particle absorbers in the high luminosity interaction regions (IRs) and sample the energy deposited near the maxima of the hadronic/electromagnetic showers in these absorbers. The ionization chambers are instrumented with low noise, fast pulse-shaping electronics to be capable of resolving individual bunch crossings at 40 MHz. In this paper, we report the initial results of our second test of this instrumentation in a super proton synchrotron (SPS) external proton beam. Single 300 GeV protons are used to simulate the hadronic/electromagnetic showers produced by the forward collision products from the interaction regions of the LHC. The capability of instrumentation to measure the luminosity of individual bunches in a 40 MHz bunch train is demonstrated. Index Terms--Gas monitor, ionization detector, luminosity monitor, shower detector.

The LHCf experiment is one of the LHC forward experiments. The aim of LHCf is to provide critical calibration data of hadronic intraction models used in air shower simulations. The LHCf has completed the operations for p-p collisions with a collision energy of √s = 0.9 and 7 TeV p-p in 2010 and for p-Pb collisions with a collision energy per nucleon of √sNN = 5.02. The recent LHCf result of forward neutron energy spectra at 7 TeV p-p collision and forward π0 spectra at p-Pb collisions are presented in this paper.

The LHCf experiment is a CERN experiment dedicated to forward physics which is optimized to measure the neutral particle flow at extreme pseudo-rapidity values, ranging from 8.4 up to infinity. LHCf results are extremely important for the calibration of the hadronic interaction models used for the study of the development of atmospheric showers in the Earth atmosphere. Starting from the recent run of proton-Lead nucleus interactions at LHC, the LHCf and ATLAS collaborations have performed a common data taking which allows a combined study of the central and forward regions of the interaction. The latest results of LHCf, the upgrade of the detectors for the next 6.5 TeV + 6.5 TeV proton–proton run and the status of the LHCf-ATLAS common activities are summarized in this paper.

This paper discusses the criteria that have been adopted to optimize the signal processing in a shower detector to be employed as a large hadron collider (LHC) beam luminosity monitor. The original aspect of this instrument is its ability to operate on a bunch-by-bunch basis. This means that it must perform accurate charge measurements at a repetition rate of 40 MHz. The detector must withstand an integrated dose of 100 Grad, that is, two to three orders of magnitude beyond those expected in the experiments. To meet the above requirements, an ionization chamber consisting of several gaps of thickness 0.5 mm, filled with a gas that is expected to be radiation resistant, has been designed. Crucial in the development of the system is the signal processing, as the electronics noise may set the dominant limitation to the accuracy of the measurement. This is related to two aspects. One is the short time available for the charge measurement. The second one is the presence of a few meter cable between the detector and the preamplifier, as this must be located out of the region of highest radiation field. Therefore, the optimization of the signal-to-noise ratio requires that the best configuration of the chamber gaps be determined under the constraint of the presence of a cable of nonnegligible length between and detector and preamplifier. The remote placement of the amplifying electronics will require that the front-end electronics be radiation hard, although to a lesser extent than the detector. Index Terms--Cold resistance, low-noise signal processing, multigap ionization chamber.

The front IR quadrupole absorbers (TAS) and the IR neutral particle absorbers (TAN) in the high-luminosity insertions of the Large Hadron Collider (LHC) each absorb approximately 1.8 TeV of forward collision products on average per pp interaction (~235 W at design luminosity of [10.sup.34] [cm.sup.-2] [s.sup.-1]). This secondary particle flux can be exploited to provide a useful storage ring operations tool for optimization of luminosity. A novel segmented, multigap, pressurized gas ionization chamber is being developed for sampling the energy deposited near the maxima of the hadronic/electromagnetic showers in these absorbers. The system design choices have been strongly influenced by optimization of signal-to-noise ratio and by the very high radiation environment. The ionization chambers are instrumented with low-noise, fast, pulse-shaping electronics to be capable of resolving individual bunch crossings at 40 MHz. Data on each bunch are to be separately accumulated over multiple bunch crossings until the desired statistical accuracy is obtained. At design luminosity, approximately 2 x [10.sup.3] bunch crossings will suffice for a 1% luminosity measurement. In this paper, we report the first experimental results of the ionization chamber and analog electronics. Single 450-GEV protons from the SPS at CERN are used to simulate the hadronic/electromagnetic showers produced by the forward collision products from the interaction regions of the LHC. Index Terms--Ionization chamber, luminosity monitor, shower detector.

LHCf is a small detector installed at LHC accelerator to measure neutral particle flow in the forward direction of proton -proton (p - p) and proton -nucleus (p - A) interactions. Thanks to the optimal performance that has characterized the last years’ running of the LHC collider, several measurements have been taken since 2009 in different running conditions. After data taking for p - p interactions at √s = 900 GeV, 2.76 TeV and 7 TeV and proton - Lead nucleus (p -Pb) at √sNN = 5.02 TeV (energy of a couple of projectile and target nucleons in their center of mass reference frame), LHCf is now going to complete its physics program with the 13 TeV p - p run foreseen in 2015. The complete set of results will become a reference data set of forward physics for the calibration and tuning of the hadronic interaction models currently used for the simulation of the atmospheric showers induced by very high energy cosmic rays. For this reason we think that LHCf is giving an important contribution for the study of cosmic rays at the highest energies. In this paper the experiment, the published results and the current status are reviewed.

LHCf is planning to measure very forward particle emission in the LHC p-Pb collisions foreseen at the end of 2012. The measurement is expected to constrain the nuclear effect in the forward particle emission relevant to the CR-Air interaction. Model discrimination power of this measurement is presented together with some detail in technical feasibility.

The Large Hadron Collider forward (= LHCf) experiment has successfully finished the first phase of data taking at LHC √s = 0.9 and 7 TeV proton-proton collisions in 2010. As current status, we concentrate on analyzing the obtained data. As the first result, the energy spectra of photon measured by LHCf during = 7 TeV p-p collision has been published recently. Also the study of the upgraded version of LHCf detector for future = 14TeV run scenario is developed with the GSO scintillator. Another possible plan of p-A(nuclear) collision in LHC is also studied. In this paper, as the current status of the experiment, analyses, and works for foreseen detector upgrade are summarized.

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