CERN Accelerating science

Solar axion flux spectrum at Earth, originating from the Primakoff process (dashed line) and from processes involving electrons (solid line), bremsstrahlung and Compton processes. We have chosen illustrative values of $g_{ae}=10^{-13}$ and $\gagamma=10^{-12}~{\rm GeV}^{-1}$, corresponding to DFSZ axions with $f_a=0.85\times 10^9$~GeV, $C_e=1/6$ and $C_\gamma=0.75$. For better comparison, the Primakoff flux has been scaled up by a factor of 100.

Comprehensive ALP parameter space, highlighting the three main front lines of direct detection experiments: laser-based laboratory techniques, helioscope (solar ALPs and axions), and microwave cavities (dark matter axions). The blue line corresponds to the current helioscope limits, dominated by CAST~\cite{Andriamonje:2007ew,Arik:2008mq} for practically all axion masses but for the $m_a \sim 0.85-1$ eV exclusion line from the last Tokyo helioscope results\cite{Inoue:2008zp}. Also shown are the constraints from horizontal branch (HB) stars, supernova SN1987A, and hot dark matter (HDM). The yellow ``axion band'' is defined roughly by $m_a f_a\sim m_\pi f_\pi$ with a somewhat arbitrary width representing the range of realistic models. The green line refers to the KSVZ model ($C_\gamma\sim-1.92$).

Possible conceptual arrangement of the NGAH. On the left we show the cross section of the NGAH toroidal magnet, in this example with six coils and bores. On the right the longitudinal section with the magnet, the optics attached to each magnet bore and the x-ray detectors.

Possible conceptual arrangement of the NGAH. On the left we show the cross section of the NGAH toroidal magnet, in this example with six coils and bores. On the right the longitudinal section with the magnet, the optics attached to each magnet bore and the x-ray detectors.

noimgValues of the relevant experimental parameters representative of CAST-I, as well as to the four possible scenarios for a future NGAH referred in the text for which the sensitivity is calculated. Numbers shown for the figures of merit are relative to CAST-I, i.~e.~$f^* = f / f_{\rm CAST}$, and are approximate.

LEFT: The parameter space for hadronic axions and ALPs. The CAST limit, some other limits, and the range of PQ models (yellow band) are also shown. The blue lines indicate the sensitivity of the four scenarios discussed in the text and table 1. RIGHT: The expected sensitivity regions of the four same scenarios in the parameter space of non-hadronic axions with both electron and photon coupling. In GUT models $C_\gamma$ is fixed to $0.75$ and we show the bound on the electron coupling ($C_e$) from red giants (dashed line along the diagonal) and the region motivated by WD cooling (orange band). DFSZ models lie below the horizontal line $C_\gamma C_e< 0.25$.

LEFT: The parameter space for hadronic axions and ALPs. The CAST limit, some other limits, and the range of PQ models (yellow band) are also shown. The blue lines indicate the sensitivity of the four scenarios discussed in the text and table 1. RIGHT: The expected sensitivity regions of the four same scenarios in the parameter space of non-hadronic axions with both electron and photon coupling. In GUT models $C_\gamma$ is fixed to $0.75$ and we show the bound on the electron coupling ($C_e$) from red giants (dashed line along the diagonal) and the region motivated by WD cooling (orange band). DFSZ models lie below the horizontal line $C_\gamma C_e< 0.25$.

The barrel toroid of the ATLAS experiment at CERN. The huge dimensions of the magnet can be appreciated by a comparison to the man standing at the bottom of the photo. The NGAH magnet's volume will be about 1--2 \% of this enormous magnet. Courtesy of the ATLAS experiment.

An example for a possible toroidal NGAH magnet design. The cross-section of the toroidal magnet with 8 racetrack coils is shown on the left side of the figure and the modulus of the field inside the coils is represented on the right side, where a zoom of the inner (upper right hand side) and outer (lower right) coils is shown. In this possible design, the coils have a double layer geometry with 18 turns in each layer. The peak field is on the inner coil's internal side (with respect to the aperture) and is 6.1 T. The calculation was done with the CERN field computation program ROXIE 10.2.

The AMS superconducting magnet. The two largest coils generate the dipolar field while the 2 $\times$ 6 shielding coils close the magnetic flux and reduce considerably the fringe fields. Source: http://www.ams02.org/what-is-ams/tecnology/magnet/scmagnet/

Left: Critical surface of NbTi superconductor. Also shown are the load line (continuous straight line, divided to two parts). The operational margin at a constant temperature is the red portion of the load line, while the working point is at the end of the black portion of the load line. Right: Critical current density of NbTi at 1.9 K (black line), together with the linear approximation for the critical current density (red line), the load line and the working point. These images represent data taken from the LHC main dipoles.

Left: Critical surface of NbTi superconductor. Also shown are the load line (continuous straight line, divided to two parts). The operational margin at a constant temperature is the red portion of the load line, while the working point is at the end of the black portion of the load line. Right: Critical current density of NbTi at 1.9 K (black line), together with the linear approximation for the critical current density (red line), the load line and the working point. These images represent data taken from the LHC main dipoles.

Left: Scheme of the 2-D readout plane of the Micromegas detectors used today in the CAST experiment. Right: Photo of the active area of a microbulk readout.

Left: Scheme of the 2-D readout plane of the Micromegas detectors used today in the CAST experiment. Right: Photo of the active area of a microbulk readout.

Left: Picture of a CAST Micromegas detector, with the x-ray window and readout electronics \cite{Abbon:2007ug}. Right: detector installed on the CAST magnet bore, surrounded by a lead cylinder, the inner part of the shielding.

Left: Picture of a CAST Micromegas detector, with the x-ray window and readout electronics \cite{Abbon:2007ug}. Right: detector installed on the CAST magnet bore, surrounded by a lead cylinder, the inner part of the shielding.

Background levels of Micromegas detectors over the years. Black points represents nominal values in CAST data taking campaigns. Squared red points correspond to data taken in special shielding conditions in the Canfranc underground laboratory.