At Snowmass 2005 the 'sources working group' recommended to choose the undulator-based source as 'save' ILC source because of its lower fatique limit (by a factor of about 2), lower thermal load on the capture systems (by a factor of about 8) and its higher capture efficiency (by a factor of about 3) at the target compared to a conventional source. More details are given here.

Concerning the deposited energy on the target and its activiation, the laser-Compton-based source may even have less technical requirements than the undulator source, because the photon energy of the laser-Compton source is much higher than that of the undulator source.

Energy deposition in the target:
A fundamental intensity limit for positron sources is given by the thermal stress which is built up in the conversion target due to the energy deposition of the particles.

Target activation and life time:
Furthermore neutrons are produced within the target (i.e. in the whole source part) which leads to a radioactive activation followed by a possible significant change in the mechanical properties of the target. The energy deposition as well as the activation have significant impact on the target lifetime.

Capture acceptance:
The capture efficiency behind the target is determined by the emittance of the positron beam and is, in particular, important for matching the acceptance of the damping ring.

The SLC positron source comes closest to a possible conventional ILC source. However, the SLC source is still a factor 60 less in flux and a factor 8 less in required energy deposition in the target.

In order to get the thermal stress under control the target has to be rotated with a tip speed of about 360 m/s. Water cooling is needed for the rotating wheel.

More details about such a possible design are given in this talk.

In the current ILC undulator target design even a wheel with a diameter of 2 m with a tip speed of 100 m/s is foreseen. Such a decrease in rotation speed to about 1000 RPM results further in a proportionally lower target stress and radiation damage.

Further details of this current undulator target design are given in this talk and are described in this EPAC06 contribution.

A Ti target has been chosen although it has a lower positron production rate by about 20% than the W target. However, Ti has a higher heat capacity by about a factor 5. In addition the mean polarization is slightly higher at a Ti (about 71%) than at a W target (about 66%) (achieved polarization for the same radiation length of 0.4 X_0), more details are given here.

The results of the simulation is that the deposited energy in the target and in the capture optics is significantly smaller for an undulator-based source compared with the conventional source.

The primary beam power for an undulator-based source is only about 40% of those of the conventional source. The percentage of the deposited energy in the target from the primary beam power is about a factor 2.4 (4) less for an undulator with 150 GeV (250 GeV) drive beam compared with the conventional source. Further details are given in this contribution to EPAC'06.

The number of produced neutrons depends on the photon energy in the target. The maximum peaks are given for of photon energy range between 15-19 MeV (right plot).

To fix the optimal drive beam energy of an undulator, that resultes in less produced neutrons, one has to calculate the energy position of the first harmonics of the undulator radiation: for the chosen undulator parameters at about 10 MeV (for 150 GeV) and at about 30 MeV (for 250 GeV), (left plot). More details are given in this talk.

Nevertheless both undulator set-ups leads to the same positron yield which is a factor 3 higher compared with the yield of the conventional source, confirming the recommendation from Snowmass'05.

Further details are given in this contribution to EPAC'06.

The rate of the neutron production is a factor 8.6 higher for a conventional source than for an undulator-based source at 150 GeV and even more than a factor 10 compared to an undulator source at 250 GeV.

The activation and dose rates are composed by contributions from the target, AMD, collimation and solenoid regions. The total resulting activation level after 5000 hours of operation of the conventional source is about a factor 67 higher than that of the undulator-based source (150 GeV). This leads to an higher dose rate (after 5000 h of operation followed by one week of shut down) by about a factor 25 of the conventional source compared with that of the undulator source.

More details about the radiation aspect of the sources are described in this EPAC06 contribution.

The maximal acceptable neutron fluxes that does not result in significant changes of the mechanical properties of the Ti-alloy target is in the range of (2-8)10^24 n/m^2. Such a flux is approximately achieved after 50000 h of operation, i.e. in about 10 years.

More details are given in this talk.

The current design features a `horizontal' remote-handling system, as used at the ISIS second target station, more details are given in this talk. Further details of the ILC undulator target under design are given in this EPAC06 contribution.

To achieve the required acceptance of the damping ring and achieve the best total capture efficiency, an adiabatic matching device (AMD) is used, starting with a magnetic field B_z=6 T that is reduced adiabatically down to a field of about 0.5 T. More details about the needed capture optics are given in this talk.

The taper parameter for the undulator source has been chosen to be g=30 m^-1 and for the conventional source g=60 m^-1.

It is therefore expected that all three sources can match the acceptance. However, the conventional source has only a small safety margin, as shown in the EUROTeV report and demonstrated in this plot for the conventional source, where the dark line marks the effciency needed to fulfill the yield requirement of 1.5.

The comparison of the capture efficiencies of the sources shows that the conventional source is expected to have a lower capture efficiency by about a factor 5 at the end of the AMD.