Dear Editors and referee.

I appreciate the referee's detailed comments. I'll respond to the referee and show you the changes in the paper.

1.Paragraph 1 on Page 1. “lower than” is not needed. “…0.69 times the nominal..” is correct.

Response; I removed “lower than” in this sentence.


2.Final line page 1. “ejected” should be “extracted” presumably.

Response; I revised “extracted” in this sentence.


3.Page 2 in relation to equation 1. It would be worthwhile to explain why relativistic effects need to be taken into account.

Response;
I have changed equation 1 to describe the Doppler shift. In the case of 200 keV hydrogen negative ion, v/c = 0.02, the relativistic effect is considered negligible.


4.On page 3, it would be worthwhile to give a reference to the conductance equations used. Have the authors assumed free molecular flow? Could they please justify the flow regime assumption?

Response;
The flow in the accelerator was assumed molecular flow. I revised the sentence and add the reference for conductance calculation.
"Assuming an average pressure of 0.2 Pa in the EG approximated by a cylindrical tube, the average free path of molecular hydrogen is 33 mm. The Knudsen number K_n is 3.3 which is reasonable the molecular flow. Therefore, the flow in the accelerator was assumed to be a molecular flow. The conductance coefficient C_{20air} for air using an ideal orifice of zero thickness and opening area A is C_{20air} = 116A (at 20$^¥circ$C, air). 
The conductance C_{mol} for a gas with molecule mass number M and temperature T is converted to C_{mol}=K sqrt{28.8/M} sqrt{T/293.15}C_{20air}. Here, the K is the the shape factor referenced by Guthrie [12] for a cylindrical tube and Dushman [13] for square shape.
The conductances of each grid were derived for the hydrogen and deuterium cases by using the model shapes shown in Table 1."
Ref 12 : A Guthrie and R. K. Wakerling, Vacuum equipment and techniques, McGraw-Hill (1949).
Ref 13 : Scientific foundations of vacuum technique ; 2nd Edition revised by J.M. Lafferty, John Wiley & Sons Inc (1962).


5.In the calculation of the throughput the filling pressure in hydrogen is 0.3Pa. This is without beam extraction I assume. Every two negative ions extracted represents a flow of one hydrogen molecule. So the operating pressure is lower when the beam is extracted. The equivalent gas throughput represented by the beam is given by: Qbeam = PdV/dt = 0.5 x dNH-/dt x kT and dNH-/dt = I/e (I is the beam current). The factor of 0.5 converts the negative ions into hydrogen molecules. For a 40A beam Qbeam ~0.5Pa m3/s. This would significantly reduce the calculated throughput of gas and alter the results. Has this been taken into account?

Response;
I have compared the density of the beam particles inside the EG aperture with the molecular density of the background. Since the density of the beam particles is sufficiently small compared to the density of the background, this calculation assumes no change in the background vacuum. I wrote the following in Page 4.
"The ratio of beam particles to background molecules is shown here. Assuming an average pressure of 0.2 Pa at the EG position, the molecular hydrogen density n_{H_2} inside the EG aperture is n_{H_2} = 4.8 ¥times 10^{19} m^{-3}. On the other hand, considering a maximum H^- current of 40 A passes through the EG, the averaged H^- current density at the EG location is 662 A/m^2 based on the size and number of EG apertures shown in Table 1. The velocity of H^- with the energy of 9 keV passed through the EG is 1.3 x 10^6 m/s. The density of H^- beam (n_{beam}) is n_{beam} = 3.3 x 10^{15} m^{-3}. Therefore, the number density of the beam is very small compared to the background molecular density (n_{beam}/n_{H_2} = 6.9 x 10^{-5}). During the actual beam operation, decrease in downstream vacuum pressure was not observed during the beam extraction. Therefore, the following beam attenuation calculations were performed under the condition that the vacuum pressure in the accelerator does not change during beam extraction.


6.In Figure 3 have the authors taken into account the non-linear potential between the PG and EG grids or is this negligible?

Response;
I add the sentences in Page 4 as "Here, the beam energy is assumed to be linear increasing. However, the actual potential curve on the center axis of the beamlet is not linear near the surface of grid because the electric field seeps into the aperture [4], which is one of the reasons for the widening of the stripping peak. However, it does not significantly affect the total number of stripping neutrals and the location of the stripping peak."