3 2009 Fermi Symposium, Washington, D.C., Nov. 2-5 energy photons in globular clusters [21-24]. The main unknowns of this scenario are the exact site of gamma- ray production (polar cap versus slot gap or outer gap), the efficiency η$_{γ}$ with which the spin-down power is converted into gamma-ray luminosity, and the to- tal number of MSPs in the cluster. The eight Galac- tic MSPs that have so far been detected by Fermi [8] have a mean spectral index of < Γ > = 1.5 ± 0.4 and a mean cutoff energy of < E$_{cut}$ > = 2.8 ± 1.8 GeV, similar to that which we found for the 47 Tuc source. Cumulative gamma-ray emission from MSPs in 47 Tuc is thus a plausible explanation for the observed signal. in 47 Tuc are equal to those of the nearby Galactic field sample, and also assuming that their average ge- ometrical correction factors ¯ f Ω are the same, we ob- tained an estimate of the total number of MSPs in 47 Tuc. Taking the mean < η$_{γ}$ > = 0.08 ¯ f Ω that we ob- tained for the sample of the nearest Galactic MSP as the most conservative estimate, we converted the ob- served gamma-ray efficiency η$_{γ}$ = 0.12 ( ± 0.05) ¯ f/N 23 for 47 Tuc into N 23 = 1.5 ± 0.6. Formally, this corre- sponds to a 95% confidence interval of 7 to 62 MSPs in 47 Tuc (assuming that uncertainties are Gaussian), which is consistent with the range of 45 to 60 MSPs estimated on the basis of X-ray observations obtained previously with Chandra [11]. The X-ray and gamma- ray constraints thus suggest a population of about 50 to 60 MSPs in 47 Tuc. This is a factor of ∼ 2 above the number of known radio MSPs in the cluster and also well above the upper limit of 30 radio MSPs estimated to be present in 47 Tuc [27], constraining the radio beaming fraction to > 0.5 times that of the gamma-ray beaming. We recall that this result relies on an esti- mate of the average gamma-ray efficiency of MSPs. We obtained this efficiency from a sample of Galac- tic field MSPs and selected the value that appears to be the least biased and that is the most conserva- tive in the sense that it produces the largest estimate for the number of MSPs in 47 Tuc. The smallness of the gamma-ray sample of MSPs, however, implies that the average gamma-ray efficiency is still uncertain and likely biased. Under this hypothesis, we estimate η$_{γ}$ from the gamma-ray flux of 47 Tuc by taking the average spin- down power to be < ˙ E > = 1.8 ( ± 0.7) × 10 34 ergs s − $^{1}$. Keeping the total number of MSPs in 47 Tuc as a parameter of the solution, for a distance to 47 Tuc of 4.0 ± 0.4 kpc [10], the measured energy flux of 2.5 ( ± 0.4) × 10 − 11 ergs cm − 2 s − 1 converts into an isotropic gamma-ray luminosity of L$_{γ}$ = 4.8 ( ± 1.2) × 10 34 ergs s − $^{1}$. This results in η$_{γ}$ = 0.12 ( ± 0.05) ¯ f Ω / N 23 , where ¯ f Ω is an average geometrical correc- tion factor that accounts for non-isotropic emission [25] and N 23 is the number of MSPs in 47 Tuc in units of 23. N 23 ≥ 1 implies that 0.12 ( ± 0.05) ¯ f Ω is an up- per limit on the spin-down to gamma-ray luminosity conversion efficiency in 47 Tuc; this is consistent with the predicted conversion efficiency of 6.1% based on a model of the expected gamma-ray emission from a population of MSPs in 47 Tuc in the framework of a fully three-dimensional general-relativistic polar cap pulsar model [24]. It is also compatible with the esti- mated conversion efficiency of ∼ 10% of [26] that was derived in the framework of a space charge-limited flow acceleration polar cap model. It has been suggested that MSPs may produce relativistic magnetized winds that, when interact- ing with stellar winds or winds from other MSPs, create shocks that are capable of accelerating elec- trons and positrons into the GeV-TeV regime [28, 29]. These high-energy particles may eventually undergo inverse Compton scattering on stellar and cosmic mi- crowave background radiation, producing detectable fluxes of GeV-TeV gamma-ray emissions. The ex- pected gamma-ray emission from 47 Tuc has been modeled in this scenario by [28], who predicted 100 MeV to 10 GeV photon fluxes of the order of 10 8 pho- tons cm − 2 s − 1 and energy fluxes of the order of ∼ 3 × 10 − 11 ergs cm − 2 s − $^{1}$, which are on the order of the values we observed using the LAT. However, [28] assumed for their calculations that the total power in- jected as relativistic electrons and positrons amounts to 1.2 × 10 35 ergs s − $^{1}$, which corresponds to a mean MSP spin-down power of < ˙ E > = 5.2 × 10 35 ergs s − 1 under the assumptions that the total number of MSPs in 47 Tuc amounts to 23 objects and that the aver- age energy conversion efficiency from the pulsar winds to relativistic electrons and positrons amounts to 1% [24, 28]. This spin-down power is about a factor of 30 larger than the average spin-down luminosity of MSPs in 47 Tuc, which suggests that the gamma-ray flux es- timates of [28] are overly optimistic and that the con- tribution of pulsar wind interactions to the gamma- The conversion efficiencies of the eight Galactic MSPs detected by Fermi cover the range from 0.02 ¯ f Ω to 1.0 ¯ f Ω with a mean value of < η$_{γ}$ > = 0.14 ¯ f Ω [8], which is larger than the upper limit we derive for 47 Tuc. However, the MSPs that have been detected so far by Fermi are faint gamma-ray sources, form- ing a sample that is likely biased toward intrinsically bright objects or objects for which the beam orien- tation is favorable. Selecting only the nearest MSPs should reduce this bias, because for close objects a larger fraction of the MSP parameter space is acces- sible to Fermi. Taking only the three nearest MSPs from the Fermi sample (which also corresponds to the three nearest known MSPs) results in a mean spin- down to gamma-ray luminosity conversion efficiency of < η$_{γ}$ > = 0.08 ¯ f Ω , considerably lower than the global average. Taking the five nearest MSPs results in < η$_{γ}$ > = 0.10 ¯ f Ω . Both values are consistent with our upper limit on 47 Tuc. Thus, our data show no evidence for differences in the gamma-ray efficiencies of MSPs in globular clusters with respect to objects observed in the Galactic field. Assuming that the gamma-ray efficiencies of MSPs eConf C091122