Interferometer-based high-accuracy white light measurement of neutral rubidium density and gradient at AWAKE

The AWAKE experiment requires an automated online rubidium (Rb) plasma density and gradient diagnostic for densities between 1 and 10$\cdot$10$^{14}$ cm$^{-3}$. A linear density gradient along the plasma source at the percent level may be useful to improve the electron acceleration process. Because of full laser ionization of Rb vapor to Rb$^{+}$ within a radius of 1 mm, the plasma density equals the vapor density. We measure the Rb vapor densities at both ends of the source, with high precision using, white light interferometry. At either source end, broadband laser light passes a remotely controlled Mach-Zehnder interferometer built out of single mode fibers. The resulting interference signal, influenced by dispersion in the vicinity of the Rb D1 and D2 transitions, is dispersed in wavelength by a spectrograph. Fully automated Fourier-based signal conditioning and a fit algorithm yield the density with an uncertainty between the measurements at both ends of 0.11 to 0.46 $\%$ over the entire density range. These densities used to operate the plasma source are displayed live in the control room.Comment: 5 pages, 8 figures, EAAC2017 conference proceedin

Towards a muon collider

A muon collider would enable the big jump ahead in energy reach that is needed for a fruitful exploration of fundamental interactions. The challenges of producing muon collisions at high luminosity and 10 TeV centre of mass energy are being investigated by the recently-formed International Muon Collider Collaboration. This Review summarises the status and the recent advances on muon colliders design, physics and detector studies. The aim is to provide a global perspective of the field and to outline directions for future work

Towards a Muon Collider

A muon collider would enable the big jump ahead in energy reach that is needed for a fruitful exploration of fundamental interactions. The challenges of producing muon collisions at high luminosity and 10 TeV centre of mass energy are being investigated by the recently-formed International Muon Collider Collaboration. This Review summarises the status and the recent advances on muon colliders design, physics and detector studies. The aim is to provide a global perspective of the field and to outline directions for future work.Comment: 118 pages, 103 figure

Towards a muon collider

A muon collider would enable the big jump ahead in energy reach that is needed for a fruitful exploration of fundamental interactions. The challenges of producing muon collisions at high luminosity and 10 TeV centre of mass energy are being investigated by the recently-formed International Muon Collider Collaboration. This Review summarises the status and the recent advances on muon colliders design, physics and detector studies. The aim is to provide a global perspective of the field and to outline directions for future work

Erratum: Towards a muon collider

The original online version of this article was revised: The additional reference [139] has been added. Tao Han’s ORICD ID has been incorrectly assigned to Chengcheng Han and Chengcheng Han’s ORCID ID to Tao Han. Yang Ma’s ORCID ID has been incorrectly assigned to Lianliang Ma, and Lianliang Ma’s ORCID ID to Yang Ma. The original article has been corrected

Setup and Characteristics of a Timing Reference Signal with sub-ps Accuracy for AWAKE

We describe a method to overcome the triggering jitter of a streak camera to obtain less noisy images of a self-modulated proton bunch over long time scales (~ 400 ps to ns) with the time resolution (~ 1 ps) of the short time scale images (73 ps). We also determine that this method, using a reference laser pulse with a variable delay, leads to the determination of the time delay between the ionizing laser pulse and the reference pulse with an error of 0.6 ps (rms).We describe a method to overcome the triggering jitter of a streak camera to obtain less noisy images of a self-modulated proton bunch over long time scales ($\sim$ 400 ps to ns) with the time resolution ($\sim$ 1 ps) of the short time scale images (73 ps). We also determine that this method, using a reference laser pulse with a variable delay, leads to the determination of the time delay between the ionizing laser pulse and the reference pulse with an error of 0.6 ps (rms)

A Novel Laser Ionized Rb Plasma Source for Plasma Wakefield Accelerators

A proton driven plasma wakefield accelerator* is to be conducted at CERN by the AWAKE collaboration. Externally injected electrons are accelerated in a large gradient (~GeV/m) wakefield. The large gradient is achieved by resonant formation of the wakefield by a train of micro-bunches. Transverse modulation of a long (~12 cm) proton bunch by the self modulation instability** creates these plasma wavelength size (~1 mm) micro-bunches. This resonant mechanism brings a strict requirement on the plasma density uniformity, namely % 0.2, in order for the injected electron bunch to remain in the accelerating and focusing phase of the wakefields. We describe the plasma source*** that satisfies this requirement during the beam plasma interaction. Rb vapor with ~10¹⁵ cm⁻³ density is confined in a 10 m long 4 cm diameter, stainless-steel tube which is heated to ~200 Co by an oil heat exchanger. The access to the source during interaction is provided by custom built fast valves. The vapor is fully tunnel ionized (first e-) by a laser forming a 2 mm diameter plasma channel

Longitudinal beam dynamics and RF requirements for a chain of muon RCSs

A facility for the collision of muons offers a unique path to a compact lepton collider with an energy reach in the multi-TeV regime, well beyond the possibilities of conventional electron accelerators. However, due to the short lifetime of muons, the constraints for acceleration and collisions are very different. An extremely fast energy increase in combination with intense and ultra-short bunches is essential for a high muon survival rate and luminosity. A chain of rapid cycling synchrotrons (RCS) for acceleration from around 60 GeV to several TeV is proposed by the International Muon Collider Collaboration. We study the longitudinal beam dynamics and radio-frequency (RF) requirements for these RCSs with respect to induced voltages from intensity effects. A high synchrotron tune due to the large RF voltages is a particular challenge. We present simulation results of the longitudinal bunch distribution to determine the number of RF stations distributed over the RCS to mitigate that large tune. The impact of the induced voltages from short-range wakefields and single- as well as multi-turn beam loading is analyzed, for both fundamental and higher-order modes

Intensity Effects in a Chain of Muon RCSs

International audienceThe muon collider offers an attractive path to a compact, multi-TeV lepton collider. However, the short muon lifetime leads to stringent requirements on the fast energy increase. While extreme energy gains in the order of several GeV per turn are crucial for a high elevated muon survival rate, ultra-short and intense bunches are needed to achieve large luminosity. The longitudinal beam dynamics of a chain of rapid cycling synchrotrons (RCS) for acceleration from around 60 GeV to several TeV is being investigated in the framework of the International Muon Collider Collaboration. Each RCS must have a distributed radio-frequency (RF) system with several hundred RF stations to establish stable synchrotron motion. In this contribution, the beam-induced voltage in each RCS is studied, assuming a single high-intensity bunch per beam in each direction and ILC-like 1.3 GHz accelerating structures. The impact of single- and multi-turn wakefields on longitudinal stability and RF power requirements is analysed with particle tracking simulations. Special attention is moreover paid to the beam power deposited into the higher-order modes of the RF cavities